Quads can still bring north of $100. From what I've seen, lower end machines can be a struggle to move.
Not too long ago, I was communicating with a CL seller who had listed a bunch of stuff for sale but sold it all before I contacted him. He had a single 1.6 G5 left, and told me I could have it if I'd come get it. I passed on it since I couldn't bring myself to drive to the north side of Cincinnati for a free 1.6.
Depends on location too. Here I frequently see iBook/MacBook power supplies for anything up to the equivalent x3 $10 CAD, and they appear to sell too. Quad G5's don't seem to appear frequently in the market place here, and when they do, one would invariably be talking hundreds of euros.