I understand the motive and for sites like Etsy, charging to list certainly helps with some poor quality (it doesn't stop bad listings initially, but eventually

I understand the motive and for sites like Etsy, charging to list certainly helps with some poor quality (it doesn't stop bad listings initially, but eventually when your stuff does not sell you don't come back). However, a lot of people genuinely think what they list is good (just watch an episode of a talent show audition and see how surprised people get when you tell them they are shit). So you'll still get loads of people submitting, but you'll have the added time-sink of dealing with those people who thought they were good enough, lost the $10 and now opened a case against you on PayPal. My advice would be (if you're going down the charge route) to simply charge everyone for submission and don't give the money back whether they make it or not.