[corty]

In GCP you can configure budgets for projects (groups of resources). Budgets can issue alerts when reaching certain percentages and reconfigure or shutdown resources when exceeded.

The budget howto docs have an example to stop everything that incurs a cost on budget overrun: https://cloud.google.com/billing/docs/how-to/budgets

But as the warning says, that might delete data in storage or other resources you may want to keep paying for. For that case, you can execute a program, that shuts down everything you can get rid of, but the cost for storage and everything you forgot will continue to be billed.