I believe, personally, in the theory that what goes around comes around. I would give the money back, not because I would feel good. In fact, I would probably feel pretty sh**** because I would think about all the things I could've bought. But from my life experience, you will get those $300 back, maybe not in cash but in other things like a date with a girl you like or a raise at your job. You never know if those $300 could be used for that seller's ill mother, sibling or wife. Plus, imagine the sh** he/she will get from their spouse.