Well, two ways. First, broadly speaking across the economy, a college graduate 2000 hours a year typically produces more GDP$ to the real economy than a non-college graduate. There are a lot of caveats to that statement, but broadly it's true and that's why people will refer to education as human capital. Second (and I believe this is the more controversial claim), as a society we really do benefit from intellectuals expert in history, literature and other liberal arts and from basic research, by which I mean scientific research which has no immediately forseeable practicable application.