That's a very simplified view. Character importance is incredibly important as well; MP-10 has been reissued a million times by both Hasbro and Takara and constantly sells because he's popular. BW Megatron clearly isn't on his level however he is also an incredibly popular character, arguably more so than Ultra Magnus.

Will Megatron lose sales because of his price? Yes, obviously. But to say that he'll shelf-warm? Are you a prophet or something to make a statement like that? There are a ridiculous amount of people in his fandom with more money than sense (especially the Japanese) that will barely flinch at the price.

So what I'll say is that there is some similarities but it's not parallel.