My recent MonsterArts haul was purchased entirely from Amazon. Certain figures like Godzilla and Mechagodzilla were relatively cheap ($50-$60), but Moguera was around $70-$80. I bought him anyway and wondered why he'd never been discounted -- then I received the figure and got my answer: the thing comes loaded with alternate body parts for flying poses, alternate weapons and intricate mechanisms to switch between them, stands and environmental bases, etc. Not to mention the diecast parts and the fact that the whole thing can be disassembled and reassembled for whatever display you want.
My point is that it may only be 6" tall, but the attention to detail, articulation, translucent plastic materials, and display options make it feel almost like a really small HT figure. Hence the price.
Having that said, I can't imagine why Destoroyah would cost so much money. I assume he'll come with some sort of projectile/attack effect, plus some environmental crap. An bonus Aggregate version would be ideal because even with the projectile addition, there's no reason why this should cost more than Ghidorah. Unless they're charging extra for the more elaborate paint scheme, which kind of makes sense since the only remotely complex character they've done up until now [paint-wise] was SpaceGodzilla, but he was a regular-sized figure so the MSRP was roughly $80 for him.