there's no fixed price for that kind of products just because it's hard to evaluate. that's why the auction is the most suitable way of selling them.
More than that, hand-drawn cryptocurrency themed artworks are pretty rare. I saw that something has been sold at ModulTrade marketplace about a month ago. Won't send any links, just google if interested. Probably they have something more, who knows
funny thing,
a friend of mine is a young artist trying to make her first steps in the industry. So she told me the other day how she googled the platforms and one of them was exactly ModulTrade one. So she was satisfied with what she saw there. I am myself more photography and just tried to help her out with this. So as I've said went to goods/services section of the forum!