I think I heard that time expired Robinson R22’s can go back to the factory for a re-build to zero hour the paper work or otherwise are on paper scrap.

There is a huge difference between a helicopter and an airplane.
On helicopters most of the moving (and expensive) parts are always replaced (or overhauled) at set time limits during inspections.
The basic airframe does not have an hour limit because all the bits vital to flight (engine, transmission, bearings, rotor head, blades, etc, etc.) have already been replaced at their designated life limit.

BTW: The going price for a good flying Bulldog over here is $60-80,000 (30-40,000 pounds).

BTW II: Re: Cessnas…you see some in Trade-A-Plane with 10,000 hours…or more. Usually former pipeline patrol aircraft and the like. I know of one guy with about that many hours on his P210.