I recently had about 100 lbs of motorola razor car chargers. There wasn't much in them. Copper in the wires was minimal, although I did get #2 for it somehow. Lots of plastic, and small low grade boards with one ic chip on them. Bits of metal too that didn't add up much. I'd say 75% of the weight was plastic at least (including wire insulation). Wall chargers might have transformers in them though...