Dan Ariely,
author of Predictably Irrational,
offered a group of subjects a choice
between 2 kinds of chocolate:
Hershey’s kisses were 1 cent.
Lindt truffles were 15 cents.

75 percent chose the truffles.
Then he did the same experiment
but reduced the price of the chocolate by one cent.
Hershey’s kisses were now free.
Lindt truffles were 14 cents.
69 percent chose the free kisses.

In his New Yorker review of
Chris Anderson’s new book,
Free: The Future of a Radical Price,
Malcolm Gladwell quotes Anderson as saying, “From the consumer’s perspective, there is a huge difference between cheap and free.”

“Give a product away, and it can go viral. Charge a single cent for it and you’re in an entirely different business… ‘Free’ has the power to create a consumer stampede.”