In my experience locally, kerosene is nearly twice the price of diesel.
Well, that's true. I don't even recall if any of my local places has kerosene at the pump. But, knowing what I know of this "farmer", he wasn't just using the kerosene in tractors, but in a fleet of diesel pickups and I bet his farm semi's too. It was "clear" kerosene....not dyed. He got it for $1.00 a gallon.... must have enough storage to get a truck load....
I think, I hope, he added supplement lubrication.....