839,000 was ex-factory price + 20,000 registration + ~7000 delivery charges - so it costs you around 870,000. i think you should get 845,000 max - most importantly you find a buyer that easily. At the end of the day its second hand. if someone has 8.5 lac why would he go for a second hand car? although its only 8 months old.
Anyways there are no fixed rules - i just shared what i think - you can always get lucky.!