Indeed, the poor economic conditions have caused a general tendency for owners to choose low operating costs so the higher end types are not selling.
An 80s Bonanza is a helluva lot of aircraft for the money nowadays if you can afford to run it. The problem is that anyone who can afford it can also afford a new(er) and more "sensible" type so the market is rather small.
If low fuel prices continue the thirsty beasts may become more attractive again.