In the long run, the killer app on nostr is probably Bitcoin.

nostr feels like the early world wide web now, except there's lightning. But we know how the web ended up. The web never really had such fluidity with payments though.

I think relay ops will need to paywall features such as likes. And long term storage. We might break even doing stuff like that. There's nothing relay ops can do to lock users in. That's why I think this all still works in the end.

In the near term you might be right about poor incentives for building clients.