Wreckers charge core charges to get the core stuff back so that it can be sent to scrap rather than put in the landfill. Its our way of helping with the environment. The scrap dealers recycle the steel for reuse. Copper, aluminum, cast all gets recycled and wreckers can do it in bulk and are paid for the recycling, if you brought a load of just scrap in would probably not be paid for it so it is not usually worth your time so it ends up in the landfill or dumped in a back alley. I sell batteries for rebuild but in bulk, engines are sent for rebuild thru my core guy down to the US if they are not rebuildable they go to Navajo and get chipped down and recycled. Sometimes there are reusable parts in the core stuff returned. If we didn't get core diffs back we couldn't sell just axle shafts or ring and pinions, the consumer would need to buy whole axle assemblies - not everything gets destroyed when a diff blows up and what does gets sent for recycling and whats good can be resold. Transmission and Transfer cases can be sold in pieces (ie people looking for input shafts or gears to do their own rebuild). I also sell my transmissions and t-cases to transmission shops for rebuild, they get new gears and seals etc. and are sold as reconditioned or refurbished at a cheaper than brand new price from the dealer. We are just doing our part recycling to help the planet. We even burn all the fluids from our Jeeps in a used oil burning furnace to keep those fluids out of the land fill.
As much as core charges may tick you off it is for the good of the planet. If you have scrap steel etc sitting around make sure it ends up in a scrap recycling bin or bring it back to the seller to get your core charge back and get it recycled. Let's do our part to help preserve the planet!
Recycle recycle recycle!