Jerky is expensive because whole cuts of beef are expensive. It seems even more expensive for jerky because the dehydration condenses the mass of the product, but when it is sold by the pound originally, all of the water weight is counted.
A pound of steak becomes a few ounces of beef jerky, and the few ounces of jerky need to cover the cost of the steak and energy required to evaporate all the water and add the tasty smoke.