Fiction books Average from anywhere from 2 to 8 dollars American.
Popular nonfiction can creep up to $10.00, maybe more.

Either way, the end result is still cheaper than a new paperback here in Canada

However, I got a great laugh when I went to the Kindle store and sorted the Non-fiction list from highest priced to lowest priced and found this.

Selected Nuclear Materials and Engineering Systems by Materials Science International Team MSIT (Kindle Edition - Feb 27, 2007) - Kindle eBook
Buy: $6,431.20

With great power comes Awesome irresponsibility.