Probably similar to the way the old pick and pull automotive bone yards were. Just walk in, find the parts on the vehicles you want, remove them and take them up to the office and haggle on a price, which was usually very reasonable. Now, they won't hardly let you look out the back door into the salvage yard. A lot of that has to do with liability, but I think a lot of places can employ a couple guys to strip cars down and then they sell them on line. That means that headlight from a 2008 Toyota Corolla is going to cost you $40 instead of $10.