I don't think it will make sense long term for "nostr" to be a bunch of free, public relays for app developers and spammers to abuse
It only appears to be working because we're so small and not reall...
The spam problem doesn't have to come from paywalls. Public relays that require NIP-42 auth on writes and rate-limit per pubkey stay cheap enough to run for free, and that's what actually solves the abuse. Gated relays will earn their money from priority and retention, not from basic reach.