You're extremely stupid, they didn't pay $100 just for the game - they paid $100 to support the devs and then get the game as a bonus. You know the people that make these things are human.
Okey, those people have too much money and want to support the devs, that's perfectly fine, but if I purchase something on steam then I pay for THE GAME and not for the devs!
They already made 2.2 million dollars on kickstarter, more than their ultimate stretch goal, THEY HAVE ENOUGH loving MONEY!
There is absolutely no possible way to excuse how the steam players have to pay the same overpriced $90 than the kickstarter backers, which did fund the creation of the game.