Actually CNN ratings have been inching up recently, for whatever reason. Maybe they have a new kitten and puppy YouTube video program on during Primetime. I don't know whether Fox News can keep the momentum. The ratings popped because of the blood in the water for the upcoming mid-terms. Now with control of Congress coming soon, the ratings may sag a little because there is less fire in the belly.
As far "pay whatever", Fox News delivers 105% of what their market viewer wants, but there is very little mainstream support for the channel. It will never break into the broader market. A particular person watches Fox News, and it isn't Joe Q. Public who doesn't watch the news much. He'll watch CNN, when he needs to. Fox News isn't a general news channel, so while they may beat CNN and MSNBC soundly, their growth is limited to their very specific, but extremely loyal, viewer demographic.