The price system features:

exchanges made only on a barter basis.

an exchange in which consumer is made better off and the producer is made worse off.

voluntary exchange that makes both the consumer and producer better off.

exchanges made in currency only.

voluntary exchange that makes both the consumer and producer better off.

Explanation:

The consumer will purchase at a price lower or equal to he is willing to pay for the good (we assume a rational person will not urchase above their willingless to do so) Thus, either has a surplus or the price is fair

The producer as well, only trades for a price above their expect to sale or that amount. Therefore it has a surplus or received what it expect.

We have determinated there is no winner or losser in trade as both parites agree voluntary without coercion.