A simple way to figure out which discount frame seems larger is by using something called the Rule of 100.

If the product’s price is less than $100, the Rule of 100 says that the percentage discount will seem larger. For a $30 T-shirt or a $15 entrée, even a $3 discount is still a relatively small number. But percentagewise (10 percent or 20 percent), that same discount looks much bigger.

If the product’s price is more than $100, the opposite is true. Numerical discount will seem larger. Take a $750 vacation package or the $2,000 laptop. While a 10 percent discount may seem like a relatively small number, it immediately seems much bigger when translated into dollars ($75 or $200).

-Contagious, p.171