I remember being on the Rebelscum forums, and people were scoffing at the idea of $50 Star Wars figures. When Anakin came out at $54, an extra $5 for the robot arm, people were freaking out.
It's been like that ever since. . . hence "$90 for the Emperor?!?! He doesn't even have any pants!!"
Way back when, The Josh (I think he was still jlcmsu or something like that) was putting forth the argument that the true cost of the figure was something like $65, and the initial figures were priced like door-busters to get people hooked on the line. . .
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. I guess that means the $90 Emperors are making up for all those Jedi Lukes, Obi-Wans, Anakins and Kit Fistos that Sideshow lost money on.