They could have an in-game market like Spiral Knights (I would love that for the metal to keys market, and Bud sellers would love that for Buds to keys) The average noob would very quickly get an idea of the market, and being able to offer unusuals to the entire community would turbocharge the economy.

Facilitating trades through Steam Wallet would be a nightmare, but who else has the authority to recover items achieved through credit card fraud? The largest problem is the idea of paying cashouts, but being able to hold that large ammount money is worthy of Visa.

This is the future of gaming. They are printing money. How many of us have dropped a grand on this game? Most of the top sellers are operating at a loss after buying keys. Ultimately, all the keys come from Valve store.