Google fucked up, and it took them days to resolve the issue. Decent customer service would offer a refund and possibly even a credit on top of that (without asking).

In my experience, Google support tends to have "the customer is always wrong" mindset.

It probably depends on how much money you're spending whether you'll get a dedicated rep who can initiate refunds without you explicitly hunting them down. $300/day is not even a spec of dust floating in a drop in the bucket to them.

A couple years ago when I was working for an advertising company that was spending several tens of thousands of dollars per day, we were offered large (hundreds of thousands of dollars) refunds on several occasions, including some where the screw-up was our own fault.