I've been doing some thinking on the D&D campaign setting I've
been working on. The players will start in a small city / large
town with a mining guild that is basically an oligarchy in the
city. The intent is to present an allegory of capitalism, where
the mining guild has all the money in the town and either controls
the government directly or has guild members in all the relevant
positions of power. They have a monopoly on the local mines, which
means they can set the prices for the raw materials coming from
those mines.

In medieval times (the time period that most D&D settings are
roughly based on), access to metal is crucial for creating all
manner of items for civilian, military, and religious life. If an
object isn't worked metal itself, the tools used to create it
are--and the source for all of this worked metal is the town
smith.

The blacksmith guild is the primary customer for the mining guild,
and just about every other trade depends on the blacksmith guild
for tools. Thus, because the mining guild has a monopoly, they'll
be charging far higher than market rates for the ore they mine.
Thus, they're getting rich while everyone in town remains poor,
struggling to pay the higher prices the blacksmiths need to charge
in order to survive. In a modern society, many people would seek
travel to a town or city with a more reasonable economy. However,
in many D&D worlds (including mine), travel is expensive and
beyond the means of the general population. Thus, the town I'm
building will be quite poor, with high prices but little wealth. I
didn't set out to have the blacksmith guild overcharging people
just to survive, but it's a useful ramification of the mining
guild having a monopoly.

There's still so much to do here, but I appreciate that these
details fit together logically.