We can break it down a little. You seem to forget I’m running one of the largest Nostr relays today.

There are seemingly two distinct mechanisms around an event’s lifetime.

1. Publishing an event (relay acceptance)

2. Persistence of an event (storage)

While more complex, I see both as distinct, and likely requiring different and simultaneously functioning approaches.

I see a few options then for relay acceptance and persistence.

1. Pay for PoW for an event (should allow broadcasting to other relays without additional payment, when above a relays min PoW acceptance). Relay may delete after a week, or may not.

2. Pay a one time fee to each relay you wish to publish to. Lightning likely isn’t suitable due to failure rate, however pre-payments or barer Bitcoin is suitable. Again, relay may delete after a week, or not.

3. Pay each for relay membership, likely providing both event publishing and event persistence. It could also offer included or extra PoW generation credits.

This PoW service can be offered by relays themselves. If you read the NIP, that’s the desirable endgame. If relays see 100,000 events a day, with $0.01 fee/event, that’s $1,000/day.

And what content relays hold and persist where they don’t get paid directly for, will ultimately be based on their paying members - if their members don’t see events they value, the relay is of no value - at least for reading/querying for those users.