The economies of this thinking came to me early in life, when I used to fly the "U control" model planes, powered by a small engine. I could barely afford to buy the engine. I happened across a price list for the parts for the engine from the manufacturer. Aha! I said to myself, I'll buy the parts and assemble it myself. When I tallied the cost of the parts separately, it was more than twice the cost of the engine whole.
Later in life in the mid '80's, a worked for an aircraft engine overhaul shop. As a sideline, and to provide a source of overhauled, on the shelf, ready to go engine parts (cylinders in particular), my boss would buy whole airplanes. I would go and pick up the plane wherever it was (as far as 1500 miles sometimes) and fly it home. His son and I would then fly the planes around for fun and errands, to the end of whatever inspection interval remained. The final flight would be to the "wrecking yard", where the plane was disassembled. My boss took the engines, his colleague took the airframes, and everything was parted out. They may very happy profits from both the engine parts, an airframe parts. Over a few years, I probably took more than twenty planes to their break up. The handy side benefit for us (me) was that on the few occasions I damaged a plane a little, we usually had the required repair parts in stock.
In part, the economies of this were a reality, in that a Cessna 150, with a 4/10 paint job, 3/10 interior, and junk avionics (let alone what maintenance it might need) was worth less as a flying plane than the cost to paint it, replace the interior and avionics. The parts were more badly needed to keep the 9/10 fleet flying. Though I'm no longer involved, that business still exists, though they only buy damaged planes now, the flying ones are finally too valuable to break up!