We have some ways of having paywalls. For instance creatr.nostr.wine where creators can put premium content behind a subscription paywall. Also nostr:nprofile1qqsvdac80utfn4gvly4fv54la0l6cp0udpptnm3ezzyajkdc44w53lgprpmhxue69uhhyetvv9ujuumwdae8gtnnda3kjctvqy28wumn8ghj7un9d3shjtnwdaehgu3wvfnsz9rhwden5te0wfjkccte9ejxzmt4wvhxjmcn8t5ut has zapit.live

nostr:nprofile1qqsrhuxx8l9ex335q7he0f09aej04zpazpl0ne2cgukyawd24mayt8gprfmhxue69uhkcmmrdd3x77pwve5kzar2v9nzucm0d5hszxmhwden5te0wfjkccte9emk2um5v4exucn5vvhxxmmd9ux73xm6 has just released a relay implementation that only allows access for those who have zapped him enough sats in the last month, which would be another interesting way of creating a paywall to access content that only exists on that relay.

Plenty of options for monetizing content, if that's your thing.