Exactly my thoughts, can not really understand how delayed alerts are acceptable... Have you managed to settle the cost with Google, what was the outcome?
Google support was surprisingly understanding, after I explained the issue. They asked some clarifying questions. Then they said that they can offer a one time refund for this case.
Since then I was paranoid not to accidentally do it again. I don't know whether GCP would refund a second time.
Amusingly enough, ingress traffic seems to always be free. So you can upload as much data as you want into their cloud, but good luck if you need to get it out.
Are the datacenters really located so close together? I assumed they weren't within walking distance of each other.