I haven't read the $7.50 price for fb articles so maybe i'm wrong:
One way for fb to make $ alike to the goog model is to "activate" key subject/nouns on users' posts. If a friend clicks on the link, the fb social network context transforms into an "indirect" search context much alike Google's search model. Ads can appear innocuously on the side. coloring scheme soft, almost not there.
This actually works better than the 2ndary model of putting up ads based on user's likes/dislikes. That's because the user initiates the inquiry rather than facebook intrusively putting up your hobbies/passions (because even though the interest is indicated, timing may *not be right). [the creepiness quotient is diminished]
This is why you should buy FB at 50 billion (or whatever they eventually agree on!)