Charisma

Charisma improves the buy/sell prices at Space Stations for both items and trade goods.

Charisma has no effect on any other kind of shop (such as Terramart) or prices of Trader NPCs.

Sources of Charisma bonuses and penalties

Armor

Bloodhound Armor (5% per piece, 15% total)

Gold Armor (15%, set bonus)

Diplomat Armor (25%, set bonus)

Clothing

Nonpareil Shirt, Nonpareil Pants, Hawker's Top, Hawker's Trousers, Toga Top, Toga Bottom (5% each)

EPP Augments

Charm Necklace (20%)

Racial

Kirhos have +25% to charisma ("Great Traders" bonus), while Pharitu have -10%, and Mantizi and Thelusians have -25% ("Poor Traders" penalty).

Other

Madness can have an unpredictable effect on how Charismatic you appear to others.

Successfully maximizing your investment in a Trade Station will also provide a trade effectiveness boost to all stations you interact with, up to a max of 10 invested stations.

The Douche Hat negates all benefits mentioned above, and penalizes with negative charisma (hardcapped at maximum -20%). Anyone willing to benefit from charisma should avoid this item like the plague.