I tested AI Studio some time back and over night now it claimed to used half of my “budget” of 20NOK (around USD $2) without me doing anything at all.
I set the billing like this since I do not trust a “open wallet” solution like this and I was right! If this event was unique you have to pay up, if this was affecting alot of user, then you get a refund.
Funny enough this project had only “Gemini API” enabled so it was easy trackable in Firebase Cloud Billing.
Heavy users have a huge job trying to find errors in usage, so do you trust your billing?