Basically we can have CDNs that ask a client to verify the viewers Nostr pubkey by sending an event.

Phase one from unauthorised to sending auth. Then you can check anything, like have they made less than 5000 requests this month. Or are they a member of my website.

Phase two is once authorised, you can ask/offer payment options - like a one time fee or become a member. Basically offer lightning invoices for payment to unlock access.

nostr:note1r94watxt6ulc8pv032ztnwsu7g4596ycwv7hryd9csyd7mzshqzs05yr5y