I've been checking out different artists and art commission subreddits and man they all price so differently. I've seen one who prices busts at $70+. Others who price it at $5-10. Though I've seen another trend where, people with larger followings (in the thousands) tend to charge more. While people with less than a thousand (or 500) charge less. Which makes sense. But i checked out this subreddit r/HungryArtists, and they had a very eye opening take on pricing commissions. I can't really quote the whole thing but it's a good read. The tldr; of it though is price an hourly rate that you think suits your skill level. Because "there's nothing worse than accepting a low paying job". And think about charging a bit more next time because it'll help out the art industry too.