I was also wondering how automated or manual you would envision the review process. I'm guessing your hope would be that the small deposit would stem the flow of submissions enough to make it all possible to review manually again, and you would also manually return all the payments sent to escrow?
Paypal/SEPA transfers are free in Europe. And even if I lived in the US and had to pay a small processor fee, I'd be more than willing to cover the $0.50 in fees if that meant I was receiving contributions from people who went through all the trouble.