I mostly believe free relays are the future.
Except content creators, most users want social media to be free.
I think free relays with revenue source like ads, promoted notes are the best way to go.
A relay, client combination can only make this happen. I think Damus is perfectly positioned to test that out (cc: nostr:npub1xtscya34g58tk0z605fvr788k263gsu6cy9x0mhnm87echrgufzsevkk5s)
Majority of users will never pay for a relay but with free relays as well a good business model can be developed. Win win for everyone.