Well, it cant, but a service could receive a bunkerlink from the creator, where the creators bunker/remote signer only allows for the automatic signage of such lists events

The creator is authorizing the relay to act on (or not) whatever particular information it receives, in order to serve content, so it's just collecting data until it meets a certain threshold. Starting out, that's zap reciepts. A (possibily close) future implementation could be that the creator tells their WoT provider that they want to send "premium" notes to only their most trusted associations. That provider could collect mutual interactions or whatever until they meet some defined threshold. At which point, that provider could send the newly approved npub to the relay, and the relay can start acting. The lockbox relay is kind of a light version of that now, serving notes to only the author's follow list. Integrating traditional payment methods could be a simple form with CC info with a spot for an npub. A relay would just need to be modified to listen for said information and the payment processor would just need to send the proof of payment + npub.