Bargaining
Bargaining is a skill used by the Thief class, or anyone who chose the "Shopkeeper's Apprentice" trait during character creation. Bargaining lowers the cost of vendor items, and makes the vendor pay more for sold ones. Bargaining, unlike most other skills, has no effect if trained past 100%.
Example
At 100% Bargaining, a vendor will only have a maximum of 10% profit. The base value of a Greater Concoction Potion is 5,000 gold. An R7 Alchemist that sells a Greater Concoction Potion will do so at 100% profit, which is <profit percentage>*<base value>+<base value> = <buying price>, (100/100) * 5,000 + 5,000 = 10,000. If bought by a character who has 100% bargaining (a maximum profit of 10%) the formula would be, (10/100) * 5,000 + 5000 = 5,500.
Lore Description
"Seller beware! A keen eye, and quick wit can convince even the stingiest merchant to undercut some of the profit they covet. The merchant princes of Tariponto make haggling an art form. The frugal can learn much from their example."