Faculty Books Recycling is a company that takes the complimentary copies of textbooks that publishers send professors, resells those comp copies to students, and makes a profit on the transaction.
Faculty Books does everything possible to make professors feel that selling - or giving away - comp copies is an ethical thing to do. In their emails soliciting textbooks from faculty (sample below), they remind potential donors of the good that textbook recycling does. It puts textbooks into students' hands at a low price. Those professors who choose to sell rather than give away their comp copies are told, "the money could sponsor a student event, be donated to charity, or spent however you like."