Help Haggle Haggling

Haggling is an indispensable skill to the trader.  It allows a
character to match wits with a merchant, seeking to get a better
price for merchandise, or to buy at the lowest possible cost.
Unfortunately, most merchants are already very skilled at haggling,
so the untrainined adventurer had best guard his treasure closely.
Thieves are natural masters at haggling, although other classes
may learn it as well.
 
See also sell, buy