I totally agree on the second point (business model alignment), however I believe that amount of requests does in a lot of cases not mean that your interests are aligned.

Examples:

* A REST API needs 3 calls for $foobar. A GraphQL API only needs 1 call. The vendor will loose money if they optimize their API in a way that you can make less calls.

* Some of your data does not frequently change. If you pay per request, you can save money by caching. However, that'll make your implementation more complex (esp. if the API is supposed to be used directly from mobile apps).

IMO it's better if the API provider can charge based on business metrics. E.g. Stripe charges based on payment volumne. It doesn't matter if you do 2 or 200 API calls to make a payment.