I've noticed that even though Sideshow polystone statues have low production runs they still don't seem to be as collectible as premium format figures. What's wrong with polystone?

Although Im not sure to what exactly you are referring too, not sure if you mean things like the Star Wars battle scenes vs. Premium format, or those failed SW smaller scenes with the Look Sir Droids/ Space Slug, or like the X-Men Sentinel diorama- (i think that was three pieces)-- or the distribution of the Bowen Statues?

But I think there are several issues-- one is-- Sideshow just does too many scales-- 1/6, 1/4, 1/2, 1/1, 1/3, 1/5 1/20th and probably more-- so many people just focus on one and go with it, and Premium Format is the one they keep most consistent over all of their properties

Also it can just be due to subject matter or poses...many pieces from many of their lines just jump all over the place in regards to pricing, or how much room they take up..

THen there is the Gentle Giant Factor, which in some cases seems like Sideshow and GG compare business plans for the year and make the same items within weeks of each other.. And alot (not all) of their polystone items are better than Sideshows versions..