truck brake drums, money makers?

I've been hearing from mechanical shops that used truck brake drums can be sold for as high as 40 dollars somewhere in the Chicago area. I looked online and could not find anything. :confused:The guys at the shops don't know where, but they have been told by other scrapers that they sell the drums to people that rebuilds them by cover them with some type of ceramic or something like that. Did any of you have heard anything like this? I am around a lot of trucking repair shops and i could use that info.