Besides, the pre-order in the PSN Store is way overpriced at 70 euros, I should be allowed to cancel it and pick up a copy elsewhere if I'm so inclined.
Pretty sure a pre-order by no means legally binds you to actually making the final purchase. It's a reservation of sorts, which in this particular case happens to give you instant access to the beta.
Absolutely. I fully intend to pick up a regular edition for 50 bucks from Media Markt or Saturn on launch day, canceling the PSN order.