Reason to pay off a no interest loan is then one doesn't have to carry insurance on the tractor.
Reason for pay off penalties is - banks borrow some of their money for fixed terms. When a customer buys a 3 year CD, that is a loan to the bank. If the bank commits to paying 2% interest for 3 years to that customer, the bank wants to be sure it can loan the money for three years at 4% (figures made up). If the money the bank loans is repaid early, the bank has to find someone else to whom to lend the money. If interest rates have changed, and the bank can only lend for 2%, then the bank loses money (after overhead). Or maybe the bank can't loan the money at all.
To me, doesn't make sense to offend, or gouge, a small customer (one buying a tractor), but on a big scale, it becomes important to the bank.
I agree with all others about reading that which is being signed. Spoken words mean nothing in that circumstance. "Fools and their money are soon parted."