Suggest passing the cost and the openai api calls through to us. eg we provide an openai api key. Just make it very easy for us to stay in control.

If your target audience is techie, you could maybe provide us a short python proxy script, that we run on our laptop, and that calls openai for you. Your website then connects to this somehow.

This would reduce load on your server, improve lag for us, and avoid cost issues for you.