nobody is forcing you to buy an unfinished game. if you want to play it, then pay the price, and if you think it's too pricy, wait until it's actually released.
alpha tests are not "HEY GUYS YOU CAN PLAY OUR GAME NOW". they're "test our stuff, but getting in this early will cost you, we need the support"
the exception was minecraft because minecraft printed money and it doesn't even count as a game.