relays are free to monetize however they’d like. @fiatjaf has an example on GitHub already that charges sats to be able to publish to that relay.
Discussion
Yes, that's exactly what I thought. Prevents spam and gives the "node" runner an incentive to keep it up and running...
Is there benefit to publishing to a specific relay?
decentralize the network. Damus’ relay is having scaling issues. If we spread the load around more evenly everything will load more quickly for all users.