From the PDF
Wealth is an expansion for the x6 game system dealing with what makes the world go round - money. It is best suited for modern settings, where money as a commodity is fluid and easily transferable, as opposed to past eras where assets were more tangible and had more or less fixed values. Wealth in a medieval game would probably take the form of gold, land or a combination of the two. In a modern setting wealth can be very variable, from hard cash and property to holding a stake in a booming corporation. This expansion attempts to deal with all those factors in abstract terms.