I've to this day never been able to pay for Gemini through the API, even though I've tried maybe 6-7 times
If you bring it up to Logan he'll just brush it off — I honestly don't know if they test these UX flows with their own personal accounts, or if something is buggy with my account.
This is my experience as well in my personal account, however at work given we were already paying for Google Cloud it was easy enough to connect a GCP account.
But somehow personally even though I'm a paying Google One subscriber and have a GCP billing account with a credit card, I get confusing errors when trying to use the Gemini API
To Logan's credit though, his team made and drove a lot of good improvements in AI studio and Gemini in general since the early days.
I feel his team is really hitting a wall now in terms of improvements, because it involves Google teams/products outside of their control, or require deep collaboration.