"I'll pay for a tractor but an ox should be free"

There is a major difference between a tractor and oxen. Yes , one's an animal and is much cheaper/weaker, etc. but all things equal, there is one important difference. Fuel. A tractor consumes a certain amount of fuel for every hour it's working, and more importantly, a certain amount in kwacha worth or fuel. No one can ask you to plough their field for free, because there is no such thing as "free" with a tractor, ever. It is a business machine and if someone wants work done, they must pay for it. In reality an oxen is the same thing, there is no such thing as free with an oxen, but because the cost is more of a fixed cost, people don't see why they should pay for it. "If my brother isn't using his oxen this morning, why can't I just borrow it for 3 hours, it won't cost him anything?"



This important difference between fixed and variable costs allows people to use tractors to earn money where they might otherwise not with an oxen.