Richard Larrick Rule of Thumb

If you are the buyer, offer the salesperson 15 percent to 20 percent less than what you can really afford ... for instance, if you absolutely can't spend more than $6,000 on a used car advertised at $7,000, try offering $5,100 (15 percent less than $6,000) ... of course you'll need to get comfortable with haggling to apply this rule, but if the seller is using the same rule in reverse for pricing the item, you almost have to haggle if you're going to get a reasonable price.