UPDATE: This information is valid for game version 1.143. You also learn an example trade route that goes around all Calradia in Warband.(All information is for the game without any mods, as mods might change the trade/economy/map in the game. In this post, you learn example price ranges and thresholds (to buy under X, to sell over Y) for the most profitable goods. Trading goods is a great way to make money in Mount & Blade: Warband.
