Note that OpenAI is notoriously terrible at pricing. Their prices are based on gut-feel and marketing, more than being priced on what customers would pay and what is profitable.

Building on top of this would be a terrible idea. The bubble is going to burst, OpenAI will stop getting investment money and will need to actually start being, you know, profitable. They will do that by milking all their actual existing customers - expect price to at least double in the following years.