$90 is the tier on Kickstarter that allowed alpha access. Why should random stragglers on Steam get a better deal than the people who allowed the game to be made in the first place? They shouldn't.
You don't want access, then move along. The final game will be much cheaper. Or you can skip it entirely.
You don't want access, then move along. The final game will be much cheaper. Or you can skip it entirely.