The purpose of the economic system is not just to provide a means of buying and selling, which is a very important part of role playing. But it also provides the means by which the towns and cities in the game earn an income and give them the resources to make long range strategic plans for improving their economic base, defenses, and offensive capabilities. 

1. Full economic system functions in the background with each port and naval base,  having a treasury with limited funds.  Funds, raised with taxes on trade and from the sale of captured ships and cargo, are used to build and upgrade forts, build warships, add new facilities, build new settlements, etc. 

2. Each ship has a ship's purse containing all prize money, trade profits, etc., which is used to repair, upgrade, and pay officers and crew.  Each captain or other character in the game has their own separate personal funds.

3. Huge list of commodities available for markets and cargo, including provisions, produce, dry goods, luxuries, and special items like artifacts, treasure chests, slaves, prisoners, etc.