Global Conquest has a "money" economic model. An infantry unit costs 25 "bucks" to raise; a typical city creates 8 bucks per turn. You can save bucks: If a city produces nothing for four turns, you can create an infantry unit on the fifth turn with 7 bucks left over. In Global Conquest, therefore, money represents real stored-up productivity.
Stars! on the other hand has a "resource" economic model. You have people on your planets, and each person produces "resource" each turn. You can also build factories; although each factory nominally produces additional resources of its own, each factory must be staffed: only as many factories as you have people will produce resources. Therefore, we can say that factories increase the absolute productivity of the people. Most importantly, you cannot store resources in Stars!. If you don't use the resources available in a turn to make something, the resources are wasted. You can't move resources either (you can move people): you can't combine the resources of two planets to produce a battleship in half the time.
One feature makes Stars! economically interesting is that you also need raw materials to make things, and the cost to mine a unit of raw materials is different on different planets. Therefore, a considerable amount of your time is spent moving raw materials from planets where materials are cheap and/or abundant to those where they are expensive and/or scarce. (One small weakness of the game is that you cannot arbitrarily reallocate resources from manufacturing to mining even at lowered efficiency: the supply curve for raw materials has a hard upper bound.)
It seems that while people in some sense know that money is an abstraction, emotionally and viscerally they think of money in the Global Conquest sense: as actual concrete productivity that has been stored up and can be used as needed. We can see this kind of thinking when we talk about the national economy as a whole: in some sense people say we don't have enough money to pay for this, that or the other (Social Security, socialized medicine, the war in Iraq, etc.). Indeed we can confidently infer that any professional economist who advocates reducing government spending during the present