All action is really exchange. What the actor prefers less is exchanged for something he prefers more, including gift-giving. It is a fallacy to say that the goods exchanged have equal value.
Salerno also covers elastic and inelastic demand.
The second in a series of ten lectures designed to introduce the layman to the basics of applied Austrian economics: "Fundamentals of Economic Analysis: A Causal-Realist Approach".
Recorded at the Mises Institute in Auburn, Alabama, on June 11, 2007.