Yeah but that is the issue. People here are arguing, they cannot trade effectively because carring their goods slows them down too much. In your example I would quest and hunt, then, seeing very cheap, -er- fur, buy it, instantely being unable to hunt any bandit that is near me. So every quest where you have to follow someone is not possible, also every quest involving prisoners and what not. The only thing you can do, is travel to the location you want to sell and hope, the price is still high enough to actually make a profit.
May point is, that people will likely not use goods to trade at all, because it's not rewarding as much, as just hunting the next group of looters.
Though in my current playthrough I kinda managed to get a decent speed right now. But I don't know how exactly I achieved it and it does not seem to be easy.
Also the question, how the AI does it, remains.