I think this is under appreciated. I run a "talk-to-your-files" website with 5ish K MRR and a pretty generous free tier. My OpenAI costs have not exceeded $200 / mo. People talk about using smaller, cheaper models but unless you have strong data security requirements you're burdening yourself with serious maintenance work and using objectively worse models to save pennies. This doesn't even consider OpenAI continuous…
Sure, if you want to let a monopoly have all the added value while you get to keep the rest you can do that.
Just make sure you're never successful enough to inspire them though, otherwise you're dead the next minute. Oops.