I don't know why every single person here insists on budget based limits. What you want is resource based limits with throttling and a calculator that takes your resource limits to determine the averaged monthly bill and a traffic spike bill.

Then the goal would be to set the resource limits to something you are happy with.

Yes, this is a pain in the ass to set up and AWS will probably never implement this, but it is the correct solution.

Because infinite downside makes the EV of using AWS infinitely negative. The biggest risk of any business using AWS is that AWS bankrupts you.