Barter

Barter is a Fallout, Fallout 2, Fallout Tactics, and Fallout 3 skill.

Fallout, Fallout 2 and Fallout Tactics
Trading and trade-related tasks. The ability to get better prices you sell, and lower prices for items you buy.Your reputation and reaction from the NPC will modify how they deal with you. If you have a good reaction with the NPC trader, you will get a better deal. If he doesn’t like you, you will pay for it – literally. Your Barter skill, however, is the primary factor, along with the Barter skill of the NPC.

Initial Level: Starting Barter skill is equal to 20% + (2% x Charisma). Average characters will have a 30% skill.

Having the "Master Trader"-perk will give you 10% bonus to this, although. The "Good Natured"-trait will give you additional 25% on the Barter skill.

Fallout 3
Initial Level (Fallout 3): 5 + ( 2 x Charisma ). S.P.E.C.I.A.L. Statistic: Charisma

The Barter skill affects the prices you get for buying and selling items. In general, the higher your Barter skill, the lower your prices on purchased items. Use this whenever you trade with a scavenger or merchant.

Van Buren
In Van Buren, as in Fallout and Fallout 2, this skill did affect store prices. However, it also represented a certain level of knowledge about the caravan houses and trading in general, giving it a small role in dialogue. The intended depth to Barter development came in the perks available at higher skill ranks.

Handel