Being a Combiner Wars Voyager, Prime is naturally capable of transforming into a torso mode to combine with any 4 Deluxe Class Combiner Wars-style toys, though his packaging call-out has him form Ultra Prime by combining him with Deluxe Class Skydive and Alpha Bravo as the arms, and with Firefly and Decepticon Drag Strip as the legs. He can combine with Sunstreaker, Mirage, Prowl, and Ironhide if one wishes to have an IDW-accurate Optimus Maximus.
Released as part of the "W Convoy" campaign ("Double" Convoy, that is!) alongside a silver chrome version of Energon Rodimus, this gold chrome "Mēki" ("plating") version of the Deluxe size Optimus Prime toy was available only as a prize in a mail-in Robot Points contest. Initially limited to 20 units in the original draw, it appears that many more were made available through toy store drawings, given how many went on to appear on online auction sites through 2005 and 2006.
Part of the first wave of the 2015 Robots in Disguise line, Optimus Prime is a smaller-scale toy. He transforms from robot to trailer/truck combination and back! Like every Robots in Disguise Legion Class toy, Optimus features 3mm posts on his hands and arms. Due to the size and simplified transformation, he ends up having 6 wheels instead of 10. His scannable Autobot insignia is on his robot mode left shoulder. However, the badge is completely impossible to scan in vehicle mode.
The toy that would ultimately end up as the original Optimus Prime toy was originally released in August 1983 as No.17 Battle Convoy from Takara's Diaclone Car Robo toyline in Japan. In 1984, Joustra released their own version (still with Diaclone sticker on the trailer) as part of their Diaclone line in Europe, either simply called Truck (according to the pack-in catalog) or Diaclone (in the pack-in comic). It's possible that GiG also released a version called Camion Convoy as part of their Trasformer line in Italy, but to this day no packaged sample has surfaced.

Released to celebrate the Year of the Goat, Platinum Edition "Year of the Goat" Optimus Prime is a redeco of Generation 2 Laser Optimus Prime, featuring the same discs lacking the G2 Autobot logo found on the Robots in Disguise Scourge version of the mold, but otherwise keeping all the electronics from the original release. Like Year of the Goat Soundwave, Year of the Goat Optimus Prime features an awkward mix of orange, black, clear pink (in some parts including missiles, the discs, and even the pump!), some clear blue (the missile's tips), translucent plastic, and some hint of chrome silver (mostly his trailer parts).
In another possible sequence of events, the trio returned to Autobot headquarters to relate their findings to Optimus Prime. The Decepticons planned to use a Destruction Beam to create a fault line near Center City, which would in turn be exploited by Rumble’s earthquake-inducing abilities to destroy the entire area. The Autobots then decided to split up in two groups, one to attack the Decepticons’ fortress, the other to stop Rumble in Center City. Optimus headed the lead team.
Since the dawn of the Transformers in 1984, the spunky little Autobot called Bumblebee has been a fan favorite. Why? He was the underdog. He was small, and he was one of the weaker Transformers, but his heart was huge and he showed great bravery on the battlefield. As a result, he was an admired and gentle friend not only to humans, but to his peers as well. And it didn’t hurt that his alternate mode was a cute little yellow Volkswagen Beetle.

Prime suffered a severe, though unfair, defeat when Megatron challenged him to one-on-one combat while imbued with the different abilities of all the Decepticons. Teletraan I, the Ark's computer, discovered the deception in time, and the Autobots were able to drive off the Decepticons. In "Prime Problem", Megatron created a clone of Optimus, which caused confusion with the other Autobots. Windcharger and Spike, however, were able to identify the clone before it led the Autobots into their demise.
Interesting work but I would like to know whether you would find the amount of new sets offered in toto has changed over the survey period. Is there an economy of scale at work? This seems to have two implications: first, the number of units for a particular set may have increased thereby affecting the price of all sets belonging to that class (but doubtful you could find exactly how many Death Star sets were produced in relation to, say, hogwarts castles); second, the popularity of certain set classes may affect what kinds of sets are available. Like with language, we are all confined to use the words we know. And so with Lego, set designers are confined to use what’s economical, unless, of course, the design calls for new styled pieces. These relations are difficult to grasp in statistical analyses, but would seem to play a role in price steering.
(translated from the Japanese Wikipedia article) The Transformers: Kiss Players was a Japan-only line of Transformers toys, manga, and audio dramas released in 2006. Kiss Players is set in an alternate Transformers universe where the Transformers are powered by the kisses of young girls. The toys themselves come packaged with small, scale figurines of the girls who power them. The toyline was openly admitted to be aimed at a specific part of the market — adults, rather than children. The comic that accompanied the Kiss Players was an unashamed reflection of this, with several images which were considered by some to be very sexually themed.
If Sparkplug suggested that the Autobots remained in their vehicle modes, he would concoct a plan where the Autobots would help evacuate the entire town in their vehicle modes. With no more than four trips in and out of the city, Optimus and the rest of the team carried out the plan without incident. The Autobots then transformed and engaged the approaching Decepticons, whom they easily dispatched. With the city safe, the Autobots moved out to help their comrades at the Decepticon fortress.
Produced to coincide with the 20th anniversary of The Transformers: The Movie and its release on DVD by Sony, this edition of Prime is a redeco of his 20th Anniversary figure. It replaces the original's metallic paint with flatter colors and does away with any and all vacuum-metalized plastic, as well as altering several other small details across the body, like the color of the lights on his feet and chest.

Optimus Prime is a redeco of Revenge of the Fallen Optimus Prime with predominately red forearms and red/silver thighs, which it was meant to be a Generation 1-inspired deco. He comes bundled with redecos of The Fallen, Megatron, Jetfire, and Starscream in a Kmart-exclusive five-pack. To date, this is the only Hasbro release of this figure that acknowledges the combining feature between Jetfire and Optimus Prime.
Though Optimus was a master marksman, he had a personal policy against shooting directly at his opponents' bodies during his races. In one such race, he allowed his rival to take the lead so that he could use his favorite weapon, the Impact Wrench Gun, to blast the road beneath the other racer's feet, causing him to lose his balance. Transform in a gust! When GT-R Megatron burst onto the scene, roaring that all previous races had failed to "ignite his warrior's spark," Optimus readied to give him the race of a lifetime. GT-R Megatron Attacks! Like other racers, GT-R Prime attended photo shoots alongside Misaki in order to promote coexistence between humans and Transformers. The Work of the GT Sister Race Queens? When a reincarnated Unicron attacked the Transformers GT finals and absorbed the huge energon pool saved up for the final prize, Prime restored his true power by using the "Matrix In" process to recombine with Misaki. Together with the other powered up racers, he fought and defeated Unicron, saving the Earth. The True TFGT
A retool of Lockdown with a new head. He is a simplified toy that can auto-transforms from an unlicensed approximation of a Lamborghini Aventador rather than a Lamborghini Centenario LP770-4 into a Voyager-sized robot by pulling out the arms first, and then flip the figure over itself. He features articulation on his arms, and features 5mm compatible hands.

Outstanding work here. After reading a number of complaints about how the price has ‘increased’ over the years, it’s great to see this analytical approach. One additional hypothesis I have is related to the increase in the number of sets released each year, which would appear to be supported by your data. More sets to buy to be ‘complete’ makes for more money out of pocket.
A redeco of the Dark of the Moon Deluxe Class toy, this Optimus Prime has large portions of his body, mostly his truck parts, vacuum metallized silver, and his light-piped eyes were neutered by blue paint. He comes with a redeco of Generation 1 Rampage's sword, which can be wield by his 5mm-compatible hands (Although not shown in the instructions). As his body, legs, and front truck kibble were chromed, care must be taken while transforming, especially with the shoulder kibble & the bottom leg's posts (This can be amended if you slightly widen the holes with 3mm hand drills). As with the original Dark of the Moon Deluxe Class figure, the instructions did not mention about forming the sleeper part until step 10, the pinky finger prevented the sword to peg down through his hands, and of course: his truck mode can attach with the Armored Weapons Platform included in the Chronicle or the Movie Trilogy Series figure. This figure has slightly loose shoulder joints.

Prime's homecoming was not all he had hoped for, for Shockwave had taken control of the planet. Prime and the other transformers were forced to go underground, waging a guerrilla war against the Decepticons. Around this time, Cobra would attempt to steal Teletran-3, but their attempt to teleport directly into the chamber would set off a catastrophic malfunction, one that threatened to crack open time itself. Optimus Prime and the Stunticons were amongst those who found themselves sent back in time. Optimus was reformatted into a 1920s semi-truck and was eventually rescued by Roadblock, Beach Head and the Baroness, who helped him capture the Stunticons.
In 2003, Transformers: Armada launched a pivotal new era in the toy line. After several lines of toys produced by one company or the other, Hasbro and Takara united to produce what was purported to be a single, identical line of Transformers for release worldwide. In tandem with this new endeavor, Armada signaled a new continuity in its accompanying animated series and a new focus in both the show and the toys on Mini-Cons, a new faction of Transformers. The Mini-Cons were much smaller robots (not much larger than humans) who were neutral in the Autobot/Decepticon fight, but due to their incredible power and abilities, were sought by both factions.
This sculpt was redecoed from the Generation 2 Gobot Firecracker. The plastic colors are a "solid" version of Firecracker's color layout, substituting opaque red for transparent red plastic. It was redecoed again for the third wave of Go-Bots to become Sideswipe (who Prime really looks a lot like), and would later be used to created Robots in Disguise R.E.V..
Part of a cross-promotion between Toyota and TakaraTomy, the deluxe-sized FJ Optimus Prime transforms into an FJ Cruiser, with his axe weapon becoming the vehicle's spare tire. The vehicle mode's body panels come packaged on the sprue, and can then be clipped onto the core figure. The mass retail release of FJ Optimus includes yellow and white panels, whilst further color variations were available when purchasing an FJ Cruiser at Japanese Toyota dealerships. As is typical of TakaraTomy exclusives, these variants came in grayscale packaging.

Of course, many voice actors have voiced him in different TV shows and video games over the years, in both English and Japanese. Most notably by a Power Rangers actor and a Batman voice actor. The latter is Will Friedle, who voiced Bee in the most recent series, Robots in Disguise, plus cameos in Rescue Bots, Transformers Prime, and the Predacons Rising TV movie. Friedle is well known as Batman’s voice in Batman Beyond. As for the Power Ranger, that would be Johnny Yong Bosch, who played Adam Park, the original Black Ranger. Bosch was Bumblebee’s voice in the video game Transformers: War for Cybertron.

Optimus Prime is then informed that Megatron has infected the core of Cybertron with dark energon and is given the task to undo the damage done. After rescuing Omega Supreme, Optimus, Ironhide, and Prowl fight their way to the core, but it's too late. The core informs Optimus that it is far too corrupted. It can repair itself by shuting down, but it will take millions of years. By that time, Cybertron will have to become cold, barren, and uninhabitable. The core gives Optimus a small piece of itself, saying it will still survive as long as the piece does. Optimus accepts the burden and the core relinquishes the Autobot Matrix of Leadership.

Optimus Prime appears in the prequel novel Transformers: Ghosts of Yesterday, where he and a group of Autobots travel in the Ark searching for the Allspark, battling Starscream's Decepticons along the way. While going through a worm hole, the Autobots find themselves encountering a group of humans in a spacecraft reverse-engineered from studying Megatron. With this discovery, Prime realizes the significance of Earth, as both Megatron and the Allspark are there. After saving Bumblebee from a pit of rock-chewing cave worms, Prime battles Starscream. He is about to be gunned down by Starscream and Bonecrusher when he is saved by the human craft. In retaliation, Starscream obliterates it.

Generation 2 Optimus Prime comes with all his original accessories, as well as two major new play features. To increase his arsenal, he is armed with a pair of black missile launchers that fit in his fists and fire red spring-loaded missiles; these launchers were retooled from the G.I. Joe figure Barricade. Secondly, he comes with an electronic "sound and lights module" that can either plug into the front of the trailer (where it resembles the air conditioners used on refrigerated trailers), or hook onto Optimus's back in robot mode (via a new slot sculpted into the cab robot). Unfortunately, the soundbox is heavy enough that doing so can easily overpower Prime's hip joints, causing him to topple backward. The soundbox features a large, vacuum metalized Autobot symbol on its front, and three grey buttons which trigger two flashing red LEDs on either side of the module, and a trio of sound effects: a truck engine noise, a laser gun sound effect and a garbled voice that said "I am Optimus Prime!". The module also features ports on either side into which the missile launchers can peg.
×