P15P28 - This
What's My Truck Worth Tech Tip might help you answer your own question, along with sage advice from TUTS 59 "As far as value, that is entirely up to you, what you're willing to pay." noted above.
The Tech Tip is more along the lines of folks wanting to offer their trucks for sale, but you can kinda flip the perspective to apply to something you are looking to buy.
PS - Your topic being a 3800 1 Ton best fits in this forum. Let us know how the possible purchase turns out.
