In a way, the "let the money decide who is a good citizen" already works. Just not in our favor: Most of the spam I receive is not from some rando using an IP I know nothing about. Its from providers that keep making good money with their current anti-abuse.. strategy. As much as I would like, I cannot refuse all mail from certain providers, because some of their customers are "important" and non-abusive. But I get the good and the bad all laundered together¹.

¹) Some do allow recipients to distinguish, e.g. Sendgrid add an X-Entity-ID header which is a stable 1:1 or <small-number>:1 map between short ascii identifiers and customers. So if you store that mapping, you can reject the usual "From: <[email protected]> but not sent using the account associated with bigcorp.example". (The way they easily could, if they cared.)