A couple months ago I collected many books from the dumpsters at Columbia and NYU. The other day I finally got around to posting a couple on Amazon, not really expecting them to sell given a presumed summertime lull in textbook sales. Lo and and behold, I am now $140 wealthier! And two more people can gain knowledge (or not, based on how pristine these books were) from the pages of those trees.
Aren't trees and trash generous!!