What a merchant will buy affects what you can barter with, too. If you're trying to barter a treasure-type item to a merchant who only buys armor and weapons, you're going to get exponentially less value out of the item. For example, I recall having a weapon worth 11 or 12k and trying to barter for a potion of return in the jade mountains. The potion was about 2600, I think, but the merchant only accepts treasure. Even though the barter was completely unbalanced, the merchant wouldn't take it.

With that example, what do you other folk figure that the ratio of barter value is for items the merchant doesn't normally purchase? 10:1? I think if it's an item that is normally purchased, the ratio is more like 1.2:1