I don't make templates, so if I have anything to sell, it would be old works, either variant design for a client who had chosen the other version, or lost contest entries.

Also if someone can afford the fee, it doesn't automatically mean that he makes better designs. Of course not. But the statistical factor of much better designs will rise for sure.

With the rippers the problem is of course harder to solve. But the fee that's being lost after the rip has been proven may also be discouraging. If moderator finds that the template has been ripped/stolen, he'll close the auction for sure. And moderating fewer, but the better exposed threads will be much more intensive.
So instead of easy $XX made on ripped design, the scammer will loose the fee. Scammers are not the enthusiasts of such "deal"

Of course the fee isn't a miraculous solution to all problems, it should work in majority of the cases, and there will be scams and rips sometimes, but they will be easier to track and more painful to the ripper, as they'll hit his wallet in the end.