I think it would be even more interesting to examine trade strategies in a game like Eve online. There's a giant simplification that occurs in games like World of Warcraft and now Team Fortress 2, where the only cost of arbitrage is the cost of finding out where opportunities exist. There are still interesting things to examine in games where transactions are instantaneous and safe, like how much risk people are willing to float by holding stock in intermediate goods, but the really interesting thing to me is examining communities where moving items around has real costs associated.

I would expect that the TF2 economy tends towards an equilibrium that is as simple as Yanis describes. This is probably not true in a game such as Eve. If one item is cheap to produce in on sector of space, and expensive in another, the equilibrium will reflect this fact: "arbitrage" opportunities will exist, and be stable, and be known by another name, "trade routes". There are real costs in transporting goods in Eve, for example the time cost of having a human pilot navigate a freighter, and the risk of being attacked by pirates.

In Eve you can have perfect information on the price and volume of transactions that occur, the movement of goods, the sovereignty of territory in which there are markets, the corporate affiliations of the people who operate firms and trade routes, and the wars and conflicts that arise between individuals and sovereign states. That sounds like an amazing playground for someone who is interested in liberal international relations, free trade and pacification, and any number of things that go beyond pure economics.