No, you're paying for the full game release - in essence you're pre-ordering and then getting to play in the first third or so of the game content early, as they continue to develop new elements and tweak/balance existing ones. Then when full release is ready you'll be patched up to full 1.0.

“Any fool can criticize, condemn and complain - and most fools do. But it takes character and self control to be understanding and forgiving.”---Dale Carnegie.