Interesting maths.
I pay the $25 or however much yearly to the Free Library of Philadelphia on top of my local library, and I'm certain I'm getting WAY more back in returns. I especially like to read eBook from the library first because then if I don't like them, they aren't "on my account" somewhere forever.
(Yes, B&N and Amazon and whatnot let you delete books, but... I... paid... money... for... that... *monkey on back*)