When you install the app you get a trial with 100,000 tokens. 1 token = 1 Open AI ChatGPT token, or 1/30 GPT-4 tokens (aligned with Open AI pricing).

The in-app purchase grants you 4 million tokens per month, with unused tokens rolling over to the next month.

My aim is to provide a sleek macOS ChatGPT/GPT-4 experience for people who wouldn't bother signing up for Open AI developer account and bringing their own API keys.

Alternatively, if there is demand, I was thinking of charging just for the convenience of my app and allowing people to "bring your own keys". Let me know if that would be a more attractive option for you. Not sure how that would fly with Apple in-app purchase policies, but could be worth a try if that's what people want.