GameShark have run an interview
with Rob McGinnis about Obsidian's latest expansion pack for Neverwinter Nights 2
Storm of Zehir's storyline involves many economical aspects. One of the reasons that you're allowed free passage around Samarach is that you earn the patronage of the leader of a powerful merchant empire; otherwise the Samarachans would greatly restrict your movement. Also, when you return to the Sword Coast, you find that the economy has been greatly weakened by the war with the King of Shadows; whether you choose to exploit this or attempt to repair the economy is up to you.
The core of the system revolves around trading raw materials to towns and cities that you come across in exchange for trade bars, which are a kind of currency that is used by various merchant guilds that you will have to interact with to advance the story. The better your relations with these merchant guilds, the better the gear you will be able to purchase from them. You will also be able to set up merchant caravans between cities, but they will also be in danger of attack from roaming monsters.
It is eerily fitting that the game centres around a troubled economy...