Yes, some relays have a per message cost. See nip-11 for wss://nostr.koning-degraaf.nl for example
> i didn't know that exists; I only have pay to use
You are correct - I meant pay to use.
I am not aware of a pay per message published relay.
Maybe nostr:npub1uac67zc9er54ln0kl6e4qp2y6ta3enfcg7ywnayshvlw9r5w6ehsqq99rx knows if this exists.
Yes, some relays have a per message cost. See nip-11 for wss://nostr.koning-degraaf.nl for example
Also cellar: https://docs.nostr.wine/cellar/readme
