You, but shorter: It can't be done perfectly in 100.0% of all possible circumstances, so better to do absolutely nothing at all. On an unrelated note, this strongly aligns with their economic interests.

For storage specifically, in that circumstance, if you weren't hellbent on claiming otherwise: it's easy to figure out what to do. For storage: block writes and reach out to the customer. Also, people are extremely unlikely to accidentally upload eg 250tb which is how you'd get to, say, $200/day. Whereas similar bills are extremely easy to accidentally create with other services.

It's totally reasonable to want spend limits firmer than AWS' discretion, which they can revoke at any point in time for any reason.