Yeah, that the main reason I never use services like Google Cloud if I don't have to, it's impossible to have a hard cap, and anyone pretending to be an expert, is just off. Google says that they can't provide a hard cap because that would mean shutting down all your services..bla bla, but at least give users the option.
We have spend caps at the billing account level and the project level (developer set) in the Gemini API now. There is up to a 10 minute delay in processing everything but this should significantly mitigate the risk here: https://ai.google.dev/gemini-api/docs/billing#tier-spend-cap...
By default, new Tier 1 paid accounts can only spend $250 in a given month.