Q: What is the "exchange value" of the D&D gold piece compared to today’s real world dollar? It would be interesting to know how wealthy our characters are, compared to modern-day prices...
A: Well, first we’d need to determine the size of a gold piece. The US Mint currently issues American Eagle uncirculated gold coins in 1/10, 1/4, 1/2, and 1 ounce sizes (or troy ounces to be more precise, a unit of measurement fairly close to an ounce that -- according to wikipedia -- was once used to measure precious metals, black powder, and gemstones… which makes it the coolest unit of measurement ever, at least in my opinion). Also according to wikipedia, the doubloon weighed in at 0.225 troy ounces, and the ducat at 0.1125 troy ounces (to use two sample coins).
So let’s generously assume a D&D gold piece contains approximately 1/4 ounce of gold (the coin itself might weigh more, depending on the purity of the coin, etc.). Taking a look at today’s prices, gold is currently trading at around $580 per ounce. That means a D&D gold piece might be considered the equivalent of roughly $145.
Now, let’s take a look at some sample character wealth. Pg. 135 of the DMG lists wealth by level. A 2nd level PC has 900gp (or $130,500), a 10th level PC has 49,000gp ($7,105,000), and a 20th level PC has 760,000gp (a whopping 110,200,000).
If you think that’s a lot of wealth, take a look at the price of goods in D&D. Let’s examine a sampling of goods we first looked at on 10/11. A mug of ale costs 4cp ($5.80), a battleaxe costs 10 gp ($1,450), a greatsword costs 50gp ($7,250), a suit of full plate armor costs 1,500gp ($217,500). How about something really pricey? A ring of three wishes costs 97,950gp ($14,202,750), a holy avenger costs 120,630gp ($17,491,350), and an iron flask costs 170,000gp ($24,650,000 -- greater than the gross domestic product of Sri Lanka)!
If these prices astound, let me crib from the 1st edition PHB: “Think of the situation as similar to Alaskan boom towns during the gold rush days, when eggs sold for one dollar each and mining tools sold for $20, $50, $100 or more! Costs in the adventuring area are distorted because of the law of supply and demand – the supply of coin is high, while supplies of equipment for adventurers are in great demand.”
True, there are a lot of assumptions in the above calculations, but there you have it! A wonderful online discussion of this very issue can also be found on this message board thread.