Folding when you have 80% equity in a 200bb pot is a ridiculously huge mistake, and I don't care how big of an edge you have in the game, you aren't leveraging that edge so much that it can overcome a mistake that big.

Considering an unknown's range that he fourbet pushes, you don't have quite 80% pot equity. More like 65-70%. So basically, in folding KK here to an unknown, you are throwing away 120-140 dollars of equity. Thats a fairly big mistake.