Martinjmpr said:A thing is only worth what someone will pay for it.
IOW I'd say until your buddy gets a higher offer his truck is "worth" $8300.
There are lots of factors that have to be considered, not only the ones already mentioned but also things like what is the economic condition of the area where he's located? (If people have low incomes they're not going to pay top dollar) and How desperate is he to sell? What is the market in his area for a pre-runner vs a 4wd (I can tell you around here a pre-runner would get minimal $$ because it's pretty much useless in snow.)