I'm trying to think how good of an idea this is, bear with me.
Yesterday I launched Just Launched and it's doing better than I ever imagined. I already have two sales!
Basically it's a startup index like any other (Product Hunt, BetaPage, BetaList, etc) but there's only one product featured per day. The product to show is either the earliest product submitted, when someone pays they skip the queue.
How does this sound - when someone is paying I show them where their payment would land them in the queue. Ie. $20 gets them to 3rd, $30 gets them to 2nd and $40 will have them featured tomorrow.