The truth is you aren't a product in either.
Users aren't products and they aren't entirely analogous to products either.

That said, paying customers on platforms like Twitter, GitHub etc… are there primarily because of the network effect. This is to say, they are there because many other people are there. What they are actually paying for is (access to) every other user.
This is why a smart strategy on these platforms is to have a large amount (the majority) of non-paying users. It's not just that some of them could pay in the future. It's that paying users are there primarily because of the non-paying ones.

This is true for Nostr paid relays too, and for other services which connect to Nostr, with the difference that you can attract paying users even if you never actually use any service that they use. For example, even if you only use free relays, as I do, you may still indirectly help paid relays to grow.

That said, on Nostr you can hide your identity rather well, if you wish, by choosing what information to associate with your account and by hiding your IP address to relays. You have a finer control than if you're using proprietary apps.