It's an interesting approach to the problem, which doesn't hurt the customer. After all, the burden of marketing has always been on the seller's side. Indeed, $100 may seem too high a fee, but the mechanism isn't set in stone either. If Valve realise that it's too difficult for indies to get in, maybe they'll reduce the entry fee, or create a secondary market with a lower one. Anyway, the customer is the winner here, and that's good.