Some of those combiner sets were never released. I think the Aerialbots were, but the Protectobot set wasn't (shame. I have a G1 Hot Spot (the fire engine that is the core/torso of Defensor) but never got the other pieces.), nor were the Stunticons it was pictured with. Similarly, the orange Constructicons were only released at the tail end of the line in a handful of markets. The rarest of the rare is a reissue of a stealth-bomber/jet fighter set that was part of G2, redone in purple and bright blue/teal and renamed as Megatron and Starscream. They were done as a test market only in a handful of stores in Ohio and nowhere else. Very few of them exist today and they're more sought after than even some prototype models that people smuggled out of Hasbro factories and offices.
Also if I'm not mistaken, the G2 Aerialbots were a collector's nightmare because large amounts of at least one of the limb bots had its body cast in a metallic gold plastic which is notorious for basically spontaneously falling apart or outright shattering under the slightest touch (and not the kind of stress fracturing that most Transformers are subject to). In that pic you posted, it's the left (camera right) arm. Whoever assembled that Superion is a brave man, because it's entirely likely that it will never come apart without exploding into a billion tiny pieces.
I have a G2 tank figure that I dare not touch anymore because it's entire undercarriage (which forms the robot mod chest) is a big chunk of gold plastic on a swivel joint and though it survived me playing with it as a kid, it can and will implode without warning now.
http://tfwiki.net/wiki/Gold_Plastic_Syndrome
The worst offender for collectors is a G1 Japanese release that's a repaint of Skorponok called "BlackZarak". Basically all of its accessories are cast in gold plastic, as are its feet. Apparently collectors have opened fresh, untouched boxes to find the figure already broken inside in spite of having never been out of the box. It's also why there's basically no such thing as a complete figure and why if you go on ebay, individual parts and pieces (like a shinpad or a gun or just a mini accessory robot's
head) will cost upwards of $50. There are reports of people buying as-mint-as-possible-in-box figures for between $1500 and $2000 when they're
still visibly broken. And these prices were from 2010-2012, so that's likely gone up since then.
Behold, the thing that will set you back a mortgage payment or two
and disintegrate before your eyes:
Wheeljack was the "mad scientist" and Ratchet the medic. Perceptor was the "scientist".
