That's like asking what the fair price would be for Land Rover.
Is it new, s/h, high or low mileage, fair or poor condition, damaged, mot'd?
Information such as history, hours a/f & engine, fit & condition all might help in your quest for an answer.
That's really weird.
Where it says "Trabant" in my post above I actually typed "Land Rover"!
Some humourous gremlins hidden in pprune's dark corners somewhere?