I know steel is expensive right now, but isn't it possible that it just doesn't cost much less to build a small tractor than a big one? I was just in a bookstore reading through one of their John Deere books and it said that when JD brought out the smaller B model, their customers expected it to be cheaper, but it cost about the same to produce as the bigger A. Apparently they had a tough time making any money on it at a price people would pay.
I don't know if this is still true, but it does stand to reason. Both big and little tractors probably take about the same number of manufacturing steps: casting, machining, stamping, painting, etc. The only difference would be the amount of material, and how much of the cost of manufacturing is due to materials? I have no idea myself.
Tom