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 25% off goods. The "Good Natured" trait will give you additional 15% on the Barter skill.

Fallout 3
Initial Level (Fallout 3): 2 + (Charisma x 2) + (Luck/2). Item Sell Value Percent (Fallout 3): 45 + ( Barter x 0.45 ). 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. You use this skill whenever you trade with a merchant or scavenger.
 * %Price rounded to nearest whole number

A Barter skill of 13 allows you to sell at 50% of the rated value of an item. As the chart above shows, each 5 point increase in score only increases sale prices by aproximatly 2.25 percent. Further increases in the skill allow further 10% increments when selling to merchants that don't have a discount for you. Barter skill does not reduce the charge for having merchants Repair your items, however.

Several items also increase your Barter skill and can be picked up off of fellow wastelanders, such as the Roving Trader Outfit (5 points) and Roving Trader Hat (5 points). Button's Wig adds 5 points to your Barter skill (and 10 to your Speech). You just have to remember to change into these outfits before starting to trade.

You can gain a permanent 1 or 2 point increase for reading copies of Tales of a Junktown Jerky Vendor.

Also, if you do Moira's River City History quest for the The Wasteland Survival Guide, she will get you a 10% discount on whatever you buy at Rivet City (and a 10% increase in what they'll pay you for whatever you're selling, so you could say it works as a local "Barter enhancer").

If you start the game by picking up everything in Vault 101 that is not nailed down, plus whatever you can pick up around Megaton (and Tenpenny Towers), and you continue to pick up whatever you can as you go along, you will spend the rest of the game stashing stuff because vendors will not have enough money or goods that you need to pay for all the loot you will have, even if you never add a single point to Barter skill. But if you keep Waiting at a caravan stop, you can cycle through the merchants until you've sold everything.

Barter is one of the lowest priority skills to which to add points... soon enough, you will have more Caps than you can use, even if it's very low.

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