It’s a business decision on AWS’s part. If they want to reduce cognitive load or objection of some customers, they’ll be more willing to “eat it”.

My strong guess is if you had a free account, setup a budget cap, went over it, and they decided to charge you*, a quick email to support would get it waived.

I’m very much a fan of AWS, in part because while they have the chance to uphold the legal terms, my experience is that they’re pretty customer friendly.

* Early on, I had many bills under $1/mo that they just comped without me having to do anything.

> Should _every_ S3 action have a `if will_incur_charges() and should_not_incur_charges(): raise Exception()` statement in it's critical path?

Budget actions work by applying an Deny All to IAM, which has essentially exactly that.

The problem is not the shutting down, it's the detection. AWS billing has a resolution measured in hours, which has limited usefulness on a platform where you can rack up thousands of dollars in charges in just a few minutes.

> Should _every_ S3 action have a `if will_incur_charges() and should_not_incur_charges(): raise Exception()` statement in it's critical path?

We're talking about one account-wide flag `has_exceeded_billing_limits`. Changes are infrequent, and can be pushed into caches. Small overruns while the flag pushes are trivially eaten by AWS.