I think this sounds easy, but it’s actually quite nontrivial in practice. You need special handling of such a limit for each kind of resource.
E.g. when my limit is reached to they remove the database, along with all backups, and all objects on S3? Since storage is billed, it should also be stopped when the limit is reached, right?
I think in practice among companies paying most of their revenue, there’d be zero interest in this, while it would be a lot of effort to implement.
This is really something specific to hobby projects, which just shouldn’t be using those “unlimited potential cost” services.