"Richard Kaplan" wrote
The only reason I can consider for an airplane to sell below its market
value would be if the seller needs to sell it quickly.

Bingo. That's the case with the last such incident I had in mind.

The only real reason to sell
below market value would be if the owner is so leveraged that he can no
longer hold that loan on the airplane

Right again.

if that is the case, then the odds
are extremely high that he also has not been in an economic position to
properly maintain the airplane.

Which is what I told the buyer. He inspected the airplane (half a day
for a twin of make and model he has never owned or maintained) and
pronounced it to be in good shape. The failures occurred as he flew
it home.

Michael