i am paying $3 / month for Twitter and i don't even go there because i can't afford to spend the time

explain how and why one should start charging for relays

Payment to an address with an npub on the transaction data. Btcpay server, go to a website, provide an npub and make a payment, that's best done with a batch payment. You could do it entirely nostr native too, DM an npub, it gives you a reply with a total and you zap that message by that amount. You could even have it send users reminders that their balance is nearing empty.