I agree with foodchain. Even in a barter economy, one needs a basic understanding of economics and the forces that drive markets. In a more sophisticated system, you need to understand how markets, supply, demand, monetary supply and policy all interact to move prices and production. Believe it or not, economics is not just the study of the above referenced measurable and quantifiable subjects, it also involves the study of people as individuals and groups to understand why they make the choices and decisions that affect the market and the economy.