Grossly misguided equation. The cost of the book is the price + the time to acquire. The benefit of the book is in the enjoyment of reading it -- which implies that readers don't see time spent reading as a "cost", unless you believe they're seeing reading as a benefit and a cost at the same time. Believe it or not, people actually enjoy the process of reading and seeing a work unfold, not just checking a completed book off the reading list.