True, but not the only method. You’d be surprised how many spammers drop with greylisting enabled.
Not really it's just a cost of doing business and if paying that cost "legitimizes" you then the ROI is probably significant.
Similar to a mafia coming to your small business and telling you you need to pay to stay open, otherwise they’ll make sure you. Still just the cost of business? Seems more like a power imbalance.