Money is a poor measurement tool. Unless you like measurement tools whose value changes every second.<p>Money is a contract; no more, no less. A unit of money essentially represents some amount of goods, services, or labor, all of which ultimately boil down to some amount of work.<p>Oh, and the value of work also varies over the long term depending on factors such as supply, demand, and perceived importance. (And in the case of humans, things like experience, education, and location).