Protect yourself how? Most cloud providers don't support any way to immediately abort spending if things get out of hand, and when running a public-facing service there are always variables you can't control.
Even if you rig up your own spending watchdog which polls the clouds billing APIs, you're still at the mercy of however long it takes for the cloud to reconcile your spending, which often takes hours or even days.
Yes, they do. You create resources and you delete resources and if you care about cost you creat alarms and tie them to scripts that automatically delete resources.
It’s basic stuff.
Those alarms can take hours to cut in, because AWS does not report costs in real time
It's true that they can but mostly they don't (particularly with "serverless" services).