Who exactly is supposed to be fired for this?

If you don’t have price controls, it’s easy to run up a bill.

If no single person had the responsibility to check the cost, then no one actually failed at their assigned job. So you either fix the system or fire everyone involved in the decision.

What you’re doing now is looking a scapegoat to beat up. You’re angry and you’re going to make someone pay for pissing you off.