It's hard to say what any "antique" tractor is worth. With a 50% undercarriage the machine should have WELL over 400 hours, or is the hour meter even working? Does it start and run well? What shape are the finals, transmission and main clutch in? How is the Radiator? Is the sheet metal straight & solid? These are some of the things to look at before determining a price, and parts for these things don't come cheap.
It all boils down to "it's worth what the buyer & seller can agree on". I have seen nice, restored D2's sell for around $5000 to $7000. Some parts machines can go for scrap metal prices. D2's that are in fair running condition can bring anywhere from $1500 to $3000.
Talk to the dealer and find out what they want for it, think about how much time and money you would be willing to put into it after purchasing ( permission from the significant other may be needed), and go from there. I have never bought a tractor that was in better shape than I thought it was in after I got it home (the excitement of the new toy hides a lot).
'46 Willys CJ2A Farm Jeep, '39 Buick sedan, '49 International KB-7, '37 Allis Chalmers WC, Cushman Scooter(s)
Antique garden tractors & outboard motors
Other rusty old junk comes & goes without warning.
The 2 most useful tools to have in your shop are a Crystal Ball and a Magic Wand