I have to agree that some engines, like an OS, are too expensive to repair in a lot of cases due to the high costs of parts.

Some people enjoy tinkering and repairing engines.

Some are very economical to repair. The Evolution engines are very economical, and Dar says that MVVS engines are too. Parts are easy to price and see for yourself.

Some 4 stroke engines are expensive to buy new, and repairs are economical.

Twins and radials would be too expensive to just chuck in trash.

A local flying friend mailed his .50SX up to W8YE to repair the port and piston damage he had inflicted. Jim cleaned up the screwdriver nicks on the liner the best he could, replaced the ring, and didn't replace the piston that was damaged from being cranked when hydrolocked. It ran fine, but had less power than before. Still, the guy was happy since he didn't have the money for parts.