Shrewd Merchant (3.5e Trait)
From D&D Wiki
You know the value of money like the back of your hand.
Benefit: You get a +2 bonus to diplomacy checks when discussing matters of a financial nature, such as haggling with a shop-keeper, or agreeing on a fee to perform an errand. In addition, you get a +2 on checks to appraise values.
Drawback: At any other time, your diplomacy checks suffer a -2 penalty, due to your miserly focus on money.
Roleplaying Ideas: Characters with this trait are often the mouth-piece for their group, negotiating the highest fees and lowest prices for the team. On the other hand, people find it hard to take you seriously, with your attention span limited to 'the next big score'.