This has always been a huge problem in MMOs. There is obviously no monitary or fiscal policy that exists, and every bit of money earned is the same as money created.
I can only think something like a tax to fund the Freeport Militia might help
[You must be logged in to view images. Log in or Register.] Or maybe some kind of assistance to the poor, based on a progressive income tax.
Alternatively, some kind of money borrowing mechanism where players can take out loans, and the interest rate be set by an algorithm determined by the cost of a certain basket of goods for sale in EC.
I'm just throwing out ideas, really.
Other ideas I've heard to solve this uniquely MMO-based problem include money decay, whereby the money slowly decreases if it is not spent. This may actually be the best, due to the quirky way money is actually created.