I'm building relay management systems with lightning payment capability that goes toward relay costs..  eventually the relays will also zap back out in various other ways.. also building out a relay directory and ways for relays to promote themselves.  relay.tools

It's hard for relays to monetize right now as it's a chicken egg problem.  You need people to join the relay, and clients tend to hide relay configuration and ship a default set of relays or run their own large central relay.  This should evolve I think, given time.