When I was younger, I borrowed money for older, used vehicles and such. The interest rate is much higher than new, for good reasons, I guess. If I default on a new car loan or new tractor loan, the repossession should net the creditor pretty good security to re-coup much or most of their investment.
If I default on an older vehicle, the risk is much higher in the creditor securing his interest in a repossession and re-sale, due to the higher risk of an older vehicle being sketchy in value and risky in possible integrity of engine/transmission, etc. The way it is. Many financial institutions have an age cut off on vehicle financing.
Paying $1000 in interest on a $8000 tractor raises the end price quite a bit.