List the 2 reasons economist favor the price system

Price system, a means of organizing economic activity. It does this primarily by coordinating the decisions of consumers, producers, and owners of productive resources. Millions of economic agents who have no direct communication with each other are led by the price system to supply each other’s wants. In a modern economy the price system enables a consumer to buy a product he has never previously purchased, produced by a firm of whose existence he is unaware, which is operating with funds partially obtained from his own savings.

It mean  additional, or one more, or sometimes one less. it's a matter of the increment, a little more or a little less, that's what the  margin  refers .