$50 isn't very much for a days work. Also if I'm doing contract work it would be nice to pitch the price to the project and my skills rather than having some arbitrary fixed price. If I have taken someone's money they will feel entitled and I have to deal with difficult clients vague requirements and suchlike. They will also (presumably) retain the rites for the code produced.
Remove the $50 and it can be just for fun. I can bail on people I don't want to work with and I can retain the code if I want to extend it or show it off on my GitHub.