Recommended read:  Virginia Postrel on the economics of donated used eyeglasses: “Recycling Eyeglasses is a Feel-Good Waste of Money”.  It turns out that the cost of screening and evaluating donated used glasses is considerably more expensive for charities than buying new glasses.  Postrel points out that “we overestimate the importance of the physical things we can see and forget about the real costs of time and attention . . .”.