Castronova the economist noted for his work on MMO's and a co-founder of TerraNova recently released a great paper analyzing the EQII economy using real data provided to him directly from Sony. It is the first instance of published, peer-reviewed, basic economic tests using actual large-scale data from a virtual world. Some important points from the paper:
"First, the virtual world we studied appears to behave in the way a real economy does. The people there are as rational (or irrational) as we are offline. As a result, there are price indexes, an inflation rate, etc. This suggests some at least rough mapping is taking place for the world's economics, and that maybe, just maybe, these worlds might serve as testbeds for economic research and policy tests.
Second, the results were not particular to one server. A natural experiment occurred in which a new server came online, and it's economic indicators quickly approached and matched those of the existing ones. This suggests the powerful role of code in shaping and directing human behaviors in the aggregate. Another point scored for Lessig.
Third, the data give a much more accurate picture of the real-world value of the assets generated and translatable via RMT markets. Updating Ted's foundational work in the space, we now find that for this world at least, the numbers are lower than previously thought--about $130-160/year, or on par with Liberia and Congo."
What I found most interesting was the documentation of massive price inflation that anyone who has played MMO's is common with. In fact it has it's own name "Mudflation" (MUD standing for Multi-User-Dungeons the sort of first MMO's in a sense). Check out these charts:
This constant increase in money supply even when player population drops (and subsequent increase in item prices as you have too much money chasing too few goods) is a big reason why usd/virtual currency prices are almost always become cheaper (the other factor being that as the game progresses you can farm/earn money at a greater speed thus reducing the labor costs of farming).