No doubt Dihutsu Rocky is a very hard core offroad machine.
I owned one for 2 years & did many hard core offroad tours like Naran,Sharan,Saif Ul Malook, Babu Sir Pass,Batogha Top,Astore,Deo Sai,Ali Malik Pass & Skardu tour on it.
Rescued Land cruiser with my rocky in deo sai, rescued many jeeps stucked in mud with her....But there is always a market value, fuel factor and seating capacity.Fair price according to model & condition of the vehicle.
Brother
I had a Dihutsu Rocky Model 1987.
First of all let me tell u I got a turbo diesel one & yours is a non turbo diesel engine 2800cc very heavy on diesel.
And what type of gear this rocky got 4speed or 5 speed?
More over the price tag is sky high...I am pasting few pictures of My 1987 model Dihutsu rocky auctioned by Sui Northern Gas Company Isb registed mint condition & I sold it for 365K (all total genuine).
Your Rocky is a body change one as this interior,front not comes in 1983 model 
In my opinion u offered him a fair price.Remember I sold my rocky in 2007 when Diesel price was less than Rs:50 a liter..
I am attaching few pics of my ride...make your decision after going through all of the above mentioned factors..























