The real cost of a commodity is the alternative that has to be sacrificed or forgone in order to purchase it. This means that when you choose to buy a commodity, you are giving up the opportunity to use that money to buy something else, or to invest it in some other way. This alternative cost is what is considered the real cost of the commodity, because it represents the true value of what you are giving up in order to acquire the commodity. It is important to consider the real cost of a commodity when making purchasing decisions, in order to make the most efficient use of your resources.