Don´t like the idea to pay for a beta.But it seems that the developers don´t care about the sense of beta. I´m not sure whether most of the people, who pre-ordered the game will really test the game and give some feedback etc. I will just wait for some test-videos etc.
Its meant to reward those who invest early interest in the game. It also helps push a few that wouldn't pre-order into doing so. However, don't forget you are not charged till the game is shipped. There's no better way of being able to try out the game (albeit in incomplete form) without actually paying for it first.
Secondly, if you've gone to the trouble of pre-ordering, and have some money invested, then you're more likely to support the beta and submit feedback then if it was just given to you. Just my opinion.