My GUESS is the same unit all new would cost you $18,000 or a bit more.
Now you could get zero percent financing for three years on a new tractor...
Buying used is saving you $3,500 to $4,000 or so. You get one year less warrenty than you would if you bought new.
How much will the financing [if you are going to finance] cost you? Add that to the cost of the used unit and compare the total to the price of a new unit with zero percent financing...
In the end you will probably win buying the used tractor. I got 230 hours on my B2910 in the first year, so 270 hours is not excessive from my perspective.