I think that if you are extremely disciplined and self-motivated you can learn a lot these days from freely available resources on the internet. I think you miss out on two really big things.
The first is that most people can learn much more and more quickly when interacting with others and with good mentors. Depending on your personality, you might need this less or be able to get some of that from communities online (e.g. forums and open source projects).
The second part is basically the value of signaling and credentials. Part of the value of a Harvard/MIT degree is that it tells potential employers that you were able to get into Harvard or MIT. Since they're very selective that is a useful piece of information for them. A capable seeking person who comes across well in interviews but is self-taught might rationally lose out to an equally smart seeking person who also has a fancy degree.
You could consider Georgia Tech's OMSCS program. It's not free but it's pretty cheap and you get a degree from a well respected school. FWIW I'm an alum of that program.