Meter based pricing works well if that is your main stream pricing model. If you are charging a subscription fee, then you should consider including a certain number of API calls in the subscription bundle. for API gateway products like AWS API gateway, tyk and otehrs, the API request based pricing is main stream. If you think API call on your platform is part of the core value, then you should consider including it in the subscription fee. If you think API call is a value added service, then you should consider charging it separately.