You're oversimplifying the problem in the other direction. Fine-grained scriptability of hard limits would bump up against all of the thorny distributed systems problems. But I do agree that fixing the simple cases is straightforward - maximum spend rates per instant and per unit of time (eg per minute, hour, day, month). Providers would shoulder the small costs from the slightly-leaky assumptions they have to make to implement those limits, and users can then operate within that framework to optimize what they want on a best-effort basis (eg a script that responds within a minute to explicitly scale resources, or a human-in-the-loop notification cycle over the course of hours so that you have the possibility to say "actually this is popularity traffic that I really do want to pay for, etc).