One sat won't cover the costs of high performance servers required to handle the load public relays will eventually be up against. The question is, how does a cheap/basically free relay raise money if it's not the client and can't push the fundraising message in front of the users? Then there's the spam problem. If a solution is forthcoming I'm all in favor. It's just a tough problem.
Discussion
"how does a cheap/basically free relay raise money..."
Free relays becoming excessively (expensively) large is counter-productive to the future of the protocol. Nostr's first strength is decentralization.
Free stuff tends to bad incentives and thus bad outcomes. Like incumbent centralized social media.
That said, there's a need for some free relays: allow people to play with the ecosystem, before they get serious and put some $ into what they value.
What does a sustainable middle ground look like, that works for both users AND relay operators? Very simple...
Read for free. Publish+store for a nominal cost. But provide something equivalent to a free trial.
Let the market take care of a) pricing and b) punishing relays that get stupid with ads and other weirdness.