A few years ago, a marketing team from a major consumer goods company came to my lab eager to test some new pricing mechanisms using principles of behavioral economics. We decided to start by testing the allure of “free,” a subject my students and I had been studying. I was excited: The company would gain insights into its customers’ decision making, and we’d get useful data for our academic work. The team agreed to create multiple websites with different offers and pricing and then observe how each worked out in terms of appeal, orders, and revenue.

A version of this article appeared in the April 2010 issue of Harvard Business Review.