If we're talking about protecting users still trying to learn the cloud, what if they mess up the setup of this cloud function?

It's worse – for us, budget alerts often arrive several hours after the fact, when you already might have burned lots of money.

Yes, well aware. I'm not sure if you actually looked at the code on that page but you have to catch the pub sub in the deployed cloud function in order to shut down billing on the project/account. This is precisely what I was referring to.

AWS has that too - you can trigger actions on budget alerts such as stopping activity https://aws.amazon.com/blogs/aws-cost-management/get-started...

What we need, a function that is AWS maintained and supported, that basically is AWS responsibility - that if it did not work - failed to shut down service that was consuming all the budget, they eat the cost.