Some variant of this topic comes up with some regularity. Leaving aside technical issues associated with implementing real-time hard caps, you still have a tradeoff. You either implement hard cutoffs which a student or someone else on a hard budget would like. Or you have a situation where an admin (or an admin who is no longer with a company) stuck some number in that seemed sensible at the time that brings down the company's whole system because of some sales spike.

I get that (and why) some people won't use AWS or its main competitors for this reason. But, frankly, they're not AWS's market and AWS will basically shrug.