You could reward the type of monetization that is correlated to high-quality content and penalize the type that is associated with spam. Site offers extra paid

You could reward the type of monetization that is correlated to high-quality content and penalize the type that is associated with spam. Site offers extra paid content or services, or takes donations? Rank up. Ads? Neutral or rank down based on type of ads. Affiliate links? Rank way down.