Your Nostr client could have a toggle for "Pay to spam me, and here's my sats-per-impression-threshold". Or it could be relay-based; maybe that better decouples the development of spam-for-sats from any particular client. Just riffing here.
Discussion
"spam" is such a fraught, dismissive word… call it something else to respect the element of free association and putting the power back in the hands of the individual. idk, maybe: "volunteer engagement", "end-run-around-ad-networks", or "rent-my-eyeballs". Come to think of it, if there's any tech that could totally dismantle Google and Facebook, disintermediating their duopoly on monetizing attention is probably key to that goal. And now this ad for a piping hot caffeine-delivery liquid medium! ☕️