ChatGPT doesn't use the API. It uses the same underlying model with a bunch of added prompts (and possibly additional fine-tuning?) to add to make it conversational.
One would pay because what they get out of chatGPT provides value, of course. Keep in mind that the users of these 2 products can be (and in fact are) different — chatGPT is a lot friendlier (from a UX perspective) than using the API playground (or using the API itself).
One would pay because what they get out of chatGPT provides value, of course. Keep in mind that the users of these 2 products can be (and in fact are) different — chatGPT is a lot friendlier (from a UX perspective) than using the API playground (or using the API itself).