Starkhaven is the largest and and most prosperous of a group of city states that are collectively strong enough to challenge any other nation in Thedas. It's wealthy enough to stand out even to a guy that has traveled across all corners of the continent. That makes it an "important city".
The page in question actually does not say there is "constant chaos" or "worthless trade," however it does say that the Free Marches provides much of Thedas' food.
"The Free Marches have no central government, no king and no capital, making the whole region difficult to protect and its economy disparate. Each city is self-governing and wary of intrusions by its neighbours, frequently leading to tensions between them as they jocky and vie for power. The government of each state also varies, the sea-port of Kirkwall, for example, is officially governed by a singular ruler in the form of the Viscount, but real political authority rests in the heads of the local chapter of The Templar Order.
During times of crisis, the most powerful merchants, generals and rulers of the Free Marches can convene to deal with the issue, similar to the Landsmeet of Ferelden."
"The region seems poorer and less organized than Ferelden: the interiors of buildings are very rustic and gangs of brigands abound (some taking over entire neighborhoods, at least by night)."
http://dragonage.wik...ki/Free_Marches