I'll be the first to say it's tempting to have my editors rate a site higher based on the program payouts. The reality though is users would figure out a pattern eventually, and we'd lose more money that way in the long run. If my logic is right, it's far more profitable to earn the users trust and earn that business for life.
Some think we focus our reviews primarily on "price/value". It does become a factor, of course. But the reality is the same site at $40/mo vs. $15/mo will only change the score by about 3-4 pts total. It can definitely be signficant in the rankings, but it's still a very small part of the overall score.
One of our top sites "Explicite" charges almost $40/mo (although recurs at $30), and they're our #11 site:
http://www.thebestporn.com/reviews_top.html