The average price for this car at nadaguides.com is $6000, while the high and low prices are $7,100 and $4,700 respectively. Given that most cars are driven an average of 12-15,000 miles per year, a car with 120-150,000 miles will be priced at least in the average range. I don't blame him for holding firm at $6,000. I may be a bit impartial since I'm also selling my '86 5-speed for $6,000.
P.S. There ARE some under 100,000 5-speeds out there, but those that own them either say they will never sell them, or that if they do, they will be asking over $10,000 for the car.