I have been testing a zap-per-feature model where people donate when we release new features. If we don't release anything, "we don't get paid" :)
It's actually not bad, considering how small Nostr is right now.
But I know most people only consider "monetization" if it is recurring an "automated". Which is a very Silicon Valley/Venture Capital way of looking at it.
Nostr companies trying to monetize are doing it in the wrong way: holding keys, closing the code, selling data, attaching paid/closed services with their clients, centralizing caching/relays, putting ads, getting a share of transactions, etc. IMO, those are all terrible ways (incentives are not aligned with users) and only serve to alienate their users against them.