Bob - I worked with Salvage yards for many years and never heard that engines where they made most of their money. Sheet Metal, and other parts make up a VERY large part of the business. Most of the time the engines get sold for scrap. By weight engines to take a large part, but the scrap metal price can be as low as $4 per ton (it was in the late 90s), a hood from a car can sell for hundreds or thousands of dollars.
The salvage yard owners in two of the stories linked (and one I didn't), said they make money from people looking for engines. Should've attributed.
At one time the Automotive Recyclers Association http://www.a-r-a.org/ were a good resource for anyone doing stories.