Annoyingly, Azure does have this capability! If your company is a Microsoft gold partner (there might be other requirements, I can't remember) then your Azure developer licenses comes with £100 free credit per month. When this money runs out, every service associated with that subscription just shuts down. It doesn't overrun, heck I don't remember even getting an email about it, they just stop until it renews the next month.

They just refuse to implement this system for non dev licenses.