But that's a little too much like the college classes which required one to sit through a tour of the syllabus on the first day. So forget that: let's dive into content.
Three weeks ago, I reached a milestone on one of my D&D projects: the economic system. That milestone was the first successful end-to-end calculation, from town and geography info all the way through to getting the price a player pays for a particular product, based on its local availability and the local availability of the kind of artisan which makes that product.
Three weeks ago, all my trade table had for each city was pig iron, the humble first step on the way to steel.
Now? Take a look:
The price that the players pay for each item on this list is the result of calculations (which I call a recipe) which specify the amount of raw materials it is made out of, and the type of artisan which makes the item. In some cases one recipe is made from another; an obvious example is that the leather pouch contains leather (tanned cowhide) as one of its ingredients.
Not all items are shown here, either: this is only finished items, which total about 50. The "74 recipes" claim at the bottom of the second picture is including partial goods; I hide those because the focus is on the things players usually want (although of course I can un-hide them.)
The key is that since each raw material and each type of artisan (or more generally, service) varies in availability from town to town, the price of each and every item will vary as the party travels.
Want to outfit your army of two hundred with swords? Get yourself to a place where iron is plentiful, because it's the primary component in the steel for those swords.
This type of system gives players a reason to go to a particular place. It also creates a source of differentiation for each town, as I can draw on the goods produced there to give an idea of what its culture is like. Most importantly, this system broadens the array of behaviors which are suitable "moves" for playing D&D. Want to be a merchant? This system supports that. Want to exercise your character's background skill in being a blacksmith or a fisherman? Go right ahead: take those fish right to the fishmonger and sell them. Or maybe you're of a more destructive bent and want to try for some industrial sabotage ... in that case, rest assured I'll update the system to reflect the chaos you've caused, so you can take advantage of the cheap prices you've engineered.
Obviously I don't have everything I want yet. I have few foods, and almost no armor and weapons. Both of those are very important. Plus I'd love to have things like furniture, and wages for men-at-arms or servants, and clothing of all kinds, and I've been meaning to throw in the calculation for rope, and oh, got to have backpacks, and I can't forget about containers (buckets, vials, sacks, flasks) to hold liquids and such. Right now, milk is BYOBucket.
So there's plenty to do. But 70-odd items is a good start.
(Credit where it's due: my economic system is based on the principles given by Alexis Smolensk over at Tao of D&D. If you haven't read him, consider it your lucky day.)