Years ago there was a thread about the supply of used CB750s drying up. I'm of the position that there are still 10s of thousands of these kinds of bikes out there. There were hundreds of thousands sold. Maybe the exhaust systems ended up in the heap, I don't think the bikes did, or got crushed either.
They just got ran into a barn, or layed up against a fence and weeds grew thru it. Great hobby for years to come!