For the ability to connect with friends and family and things that interest you, the price you pay Facebook is the opportunity for companies and groups to influence you (to buy or do something).
What it seems like is that folks are surprised that Facebook is really good at figuring how to influence people. The price for the opportunity to influence you is explicit to advertisers. It's implicit and hard to quantify from a user perspective because it's attention and time and the conversion isn't always immediate. If it was easy to price out, FB would be a subscription service. And, some users are more valuable than others.
Further, people do not care about their privacy. People definitely care about losing money and time dealing with identity theft, definitely care about fraud, anything to do with actually losing real money. But privacy, people don't really care (or know enough to care) about it.
FB has an altruistic view of wanting to connect everybody and those connections are supposed to make your life better and the world a better place. And there's nothing wrong with trying to work towards that goal.