I'm not sure that books were so cheap in the last 500 years. Many people didn't even know how to read back then. Or did they? Besides, it is questionable how many of those books of 500 years ago were good books for learning.

One most presume that the books were cheap, analphabetism were very low, and most books were truly good for the common people to understand it. I'm not sure this situation was entirely true :)