[Alisa]

I see the same discrepancy when I walk into a book store for the same kind of reasons. Publishers charge more for some books than others. New releases tend to be more. People are eager for them and will pay more to get them now rather than later. Technical & text books take a lot of work to produce and sell in low volumes so they tend to be more. Books that have been out a long time in paperback are less. They are easy to come by and have to compete with used prices. Books that are in the public domain can be resold by anybody hence they are typically quite cheap unless there is some marked added feature. Just because these books are in digital format at Amazon doesn't remove the concept of market value. Print is just one cost variable. Content has it's own value.