Are you prices fair? Sure, who's to say they're not.
Will Indie developers pay that? I doubt it, most are on tight budgets (as seen by the quantity of unpaid vs paid requests on itch.io).
Is it market-related? For a commission, perhaps. For an asset pack, no. It's far above the market.
I can pay $2 - $15 per character that is rigged, comes with animations and is pre setup in Unity at the Unity Asset Store. You're charging $80 per boss character with fewer animations, and I must set it up myself (which is no big deal for 2D, but it is an extra step).
Perhaps have a look at Fiverr. You can see what other artists are charging and whether they get much work.