hmm this is how i decide my prices; i decide on some temporary prices and then try them out on a test-run!! then when i finish any piece, i think afterwards "was my time and effort worth the money?" and if there was some frustration after finishing a commission, i raise the price until that frustration goes away! i think its a very good method because (for me!) it completely removes any stress thinking "is this a good price? should i calculate it based on hours or.." and i just end up thinking "thank god i had those prices, because this commission was sure worth completing Because of the price!"
heehee i hope it was ok sharing, i just felt like it could provide some insight, maybe!!!!