I don’t think it’s unreasonable for colleges to increase tuition when over the 4 typical years of a degree, a lot of costs are going to be rising, from salaries to physical goods, insurance etc. While I think it’s great for those colleges that lock tuition in, I’d be surprised if they haven’t budgeted it so that their total revenue over those 4 years is roughly the same as it would have been (obviously starting lower than the initial cost the student saw in freshman year). (The benefit being the paying family exactly knows their budget.) And as noted, public colleges probably have more of a buffer if they underestimate this than privates.