[ganarajpr]

THIS. This is especially true for old (and new?) academic books / works. If its really popular book, old academic books are available to buy at exorbitant prices ($100-$1000+) or alternatively you can just get it free as a pirated pdf. Guess what most people will prefer!

[rootusrootus]

You can buy old academic e-books for exorbitant prices? Are you not perhaps thinking of physical copies of out-of-print books?