Sony's lost me as a beta tester, I'm not paying real money for a beta.
The prices are not that bad and I'd love to see something like this come to all games in the PSN Store. It would be great to have the option to rent or buy the digital version of games like Watch Dogs or The Show and I think it would entice many people to move from disc to digital. If I could rent the digital version of games for around $15 for 30 days, I'd be tempted to drop GameFly.
The problem I have with them implementing the pricing now is because a beta is meant to test the software for bugs, not to start turning a profit from testers. Money is already really tight for my family so, I wouldn't be able to afford to test many games. Sony has essentially priced me out of the beta but, even if I could afford to rent many games, I have no interest in paying for a beta... ever.