Remember it's still in beta. Things can and will change according to feedback. I think some of the weekly and even a few of the monthly prices are OK. Honestly, I have bought games at full price that I finished and never touched again. Granted, that's partly my fault but a system like this can work well for me. Rent the game for a week or a month and finish it.
A subscription service is coming which should be better. They should also add a rent to own system. The service is still very young and will improve over time. Just keep sending your feedback to Sony!