Trader
From Guild Wars Wiki
A trader is a NPC, who sells and buys materials, runes or other items in exchange for gold. Unlike a merchant, a trader sells from a variable inventory at varying cost, according to supply and demand and thus reacting to the state of the game economy. A trader, unlike a merchant, does not sell and buy goods at a fixed price, but depending on supply and demand. You may even find a trader "out of stock" if there is very little supply. Prices have a lower limit (minimum sale prices are 10 gold for common materials, 100 gold for rare materials and 100 gold for Runes and Insignia; the minimum price for Celestial Sigils is unknown), but are open ended to an extent. Prices for certain Superior Runes have gone up to 100 platinum at one point, but since the maximum amount of gold you can carry on your person is 100 platinum, this is essentially upper limit.
The available traders are:
