I have no idea how much money is spent on books and hot water, but I would assume once you also roll into it the entire education program including facilities, utilities, personnel, etc, as well as technology(computers, tvs, cable, internet, etc), mental health counselors, and what ever other programs that are in place to entertain, placate, or rehab prisoners, I would think it would be a pretty big number.
Also, I know you are minimizing for the sake of your own point, but I would assume that the cost to heat water for the daily shower of a couple thousand ppl would add up really quick.