Here's a new Star Citizen trailer that explains how the economy will function in the game.
Star Citizen is an upcoming space trading and combat simulator game for the PC. It's like Eve Online but in addition to online servers it will also have a single-player campaign and customizable private server components. The game is set in a 30th-century Milky Way galaxy centered around a fictional United Empire of Earth. It will be released as an alpha quarter 4 2013.