As a point of reference, I bought an 89 last summer for $8,000 from orig owner. I thought I got a good deal. I got the tandem axle trailer with it and new tires thrown in on the deal. My interior was different then yours though. I don't have the cup holders in the motor cover and the back seat is the older looking straight bench. Overall, yours looks like it's in better shape and the asking price seems justified.
On a side note, how is your bimini folded back on the transom like that?