Which you picked up from books after getting a degree at a university that most likely taught you (or at least improved) your ability to think and learn. I think it is a bit disingenuous to say that you learned CS for far less than the tuition at a typical university after you got a degree at a typical university.
Well, to be pedantic, I didn't get a degree at "a typical university", I got a degree at a really expensive private college (courtesy of a scholarship which made it not so expensive to go). I got there by being raised to read a lot, engage in critical thinking, etc., etc., which skills were then honed over the course of four years.
Anyway, college was a boost, yes, but my main point was that one doesn't need a CS degree (and, honestly, there aren't many CS degrees out there anymore -- just Java-programming degrees masquerading as CS) to be able to do this stuff. Any sort of good liberal-arts background, even one not involving an actual piece of sheepskin from a four-year institution, should be all anyone needs to pick up CS or just about any other subject.
But the merits of a real liberal-arts education are a whole 'nother thread.
Everything I know about theoretical computer science I picked up from books, at a price far below the tuition of a typical university.