I've been regularly donating $30 every month I'm able to (which isn't as often as I'd like due to medical bills and increased living expenses in the last year) for what it's worth, on top of my KS backing. I'm sure many here do similarly, or even more. Sadly, it's the huge mass of the rest of the backers that would have to participate to make this happen.
Still, I firmly believe the game can and will be awesome - if not EVERYTHING we hoped for SIII to be - without reaching that sum. If anyone knows how to frugally micromanage a budget, it's Yu.