Does this mean it's not just for the several hundred dollar people?
No this is for the Alpha backers, maybe by "purchasers" they mean people that weren't backing this during the kickstarter phase but bought the Alpha package from their store.
I am thinking of buying into the Premium beta phase, but it is a lot of money though. Believe it comes with the DLC pack for the full game but still I am not sure I want to drop that kind of money on this game even though I really want to play it. Might have to wait and just watch youtube videos until the game comes out.