The real value in college, like just about any other pursuit, is network building. Like several commenters have said, if all you wanted out of school was to learn something, you could go to the library. The fees for college are for the intangible aspects, and are worth far more than a direct dollars-to-dollars comparison will show.
Think of college as an IDE for personal development. It sets up a ready-made environment for you to explore new relationships, indulge in a variety of pursuits, and learn about the world. There are thousands of other people using the same IDE, creating a lively place for discussion of issues you'd never otherwise think of. People introduce you to new features or mechanics which you never considered before; you naturally begin to collaborate and contribute to large scale projects. You might even lead a few. Could you get all of these experience by piecing different activities together? Of course. Would it be nearly as productive, successful, and transformational? Of course not.
Like an IDE though, sometimes college can get a little bulky; you're naturally going to be paying for some features you don't want or use. But most of us keep paying anyway, because there's a few killer features which make it all worthwhile, ones that you wouldn't dare put a pricetag on. Attending university altered the entire trajectory of my life, starting from how I saw myself to what I want to accomplish. It redefined what I thought was possible for human endurance and achievement. It restored my faith in the ability of small groups to enact large positive change. It cost a pretty penny, but it has provided an unquantifiably large return on investment.