Price per request is the most obvious one. If you had a widget solver, you could charge per widget solved. This way a one widget solve request or a csv upload

Price per request is the most obvious one. If you had a widget solver, you could charge per widget solved. This way a one widget solve request or a csv upload of a million widgets are priced accordingly. You can also charge per mb, if your service is some sort of data piping. Or if it's a ML translation service, you charge per word. That kinda thing.