When running AD&D, I've not been much for elaborating complex rules schemes. I've always felt that rulings, in the past, trump rules. However, having experienced Gangbusters for two weeks, I can now see how rules allow people to get a firm grasp on what they want their characters to do, particularly when dealing with abstract and alien concepts such as running a manor or a bootlegging business. What do these two things have in common? The players have no idea how much they're supposed to be taking in, they have no idea what "reasonable" rates look like, etc. This isn't a slight to them—they simply didn't grow up in a fantasy or Prohibition economy. The stuff is so far out of the realm of their experience that they aren't sure what constitutes good decisions. In times such as this, rules do help.
For example, Gangbusters has concrete rules that describe how much booze can be produced in a still every week, and how much that booze should go for. This is a huge boon to the criminals in my game because they need to know if they're getting a reasonable price when they sell it. Once they've determined that, they can start to make plans far in advance because they know the general status of the booze economy, as determined by the bootlegging rules.
When there are no rules to support things like this, the players have no resources to fall back on to make sure things are generally happening correctly. I know that earlier editions of D&D had more concrete domain management rules than AD&D does (ie, any) and I know that I've been designing domain management rules myself so I can present a packet of information that will allow them to function in the economy. It doesn't matter if they know that a sword is 25 gold pieces if they don't know how many gold pieces nobles regularly have to dispense. They can't decide if a job is paying a decent wage if they can't compare their wage to the jobs other mercenaries do (and the total amount that the hiring party has).
These sorts of numbers, I realize now, are important for players to have a sense of scale. Just as installing a history provides a textural background for players to latch on to, so does installing a functional economic system that they can examine. In the case of Gangbusters, these are mostly integrated with the rules. Which is good!
With that in mind, my work at fleshing out the Arunian economy (and the sub-economies of each nation and race) must continue apace.