There are always ebs and flows with prices, especially when it's a movie year as scalpers think that the most common thing will suddenly be in demand because the franchise is fresh in the laypersons mind. It's sort of the same principle that stores use when they stock toys, they always over stock (and honestly, over price) movie figures assuming that people will want to buy them because the movie is fresh in everyones minds, but prices eventually come down once the public in general "forgets" about the franchise.I think it depends on age, strength/thickness of the combiner ports/pegs, and how much weight they are holding (assuming they are standing on display rather then laying in a box in combined mode, which wouldnt be putting much strain on the limbs).
I've had CW Superion on display since release (so about 2 years?) and havent noticed any strain or sagging so I'd say modern ones should be fine.
Cant really say as much about say G1 combiners but I probably would say best to store those individually rather then combined mode.
Just my thoughts though.