Which economic principle ensures that the last unit sold provides equal value to both consumers and producers?

The principle that ensures the last unit sold provides equal value to both consumers and producers is market equilibrium. At market equilibrium, the quantity of goods supplied equals the quantity demanded. This occurs at the equilibrium price, where the price consumers are willing to pay (the marginal benefit) matches the price producers are willing to accept (the marginal cost).

In this state, the last unit sold reflects the highest price consumers are willing to pay, which is equal to the lowest price producers will accept. As a result, both parties derive the maximum benefit possible from the transaction, and no further transactions would increase the overall welfare. If the price deviates from this equilibrium, it would create either a surplus or a shortage, leading to inefficiencies in the market.

Understanding market equilibrium helps explain how resources are allocated in a way that maximizes efficiency and satisfaction for both consumers and producers, with the last unit sold ideally reflecting this balance.