Important to remember that nostr simply relays notes and other stuff, from one user to another.  That will always be valuable.  It does not STORE data, there's other solutions for that, which are not nostr.  The storage market (e.g. for notes, and other stuff, which actually was written in the original web proposal) will always be 1,000-1,000,000 times bigger.  So nostr has a total addressable market of maybe 0.01% of the web.  That is perfectly OK.  The challenge is not, and will never be to grow nostr to 500million users.  The challege is to spread ideas such as zaps, or ability to move from one app to another, or an app eco system, to the wider web.  Nostr then provides realtime payments, which is the cherry on top.