One man's trash

Eric likes to pick things up.  Off the street, I mean.  He collects rocks, sticks, small pieces of plastic and metal, empty eyedrop bottles, Christmas light hangers, and all kinds of trash.  Every time we walk across a parking lot, he has to stop to pick something up.  A while back I asked him, "Eric, why do you pick up so much trash?"

He looked at me, a little hurt, and explained, "Sometimes it's treasure."