The author has shares this information in a new book
"Predictably Irrational: The Hidden Forces That Shape Our Decisions."
Why you're a big sucker
Question: What's one of our biggest, most illogical weaknesses as consumers?
A. "Free" offers. When the price of something is said to be zero, it blinds us. We get so excited, we fail to realize that we'll end up paying in some way.
Question: For instance?
A. When I bought a car a few years ago, I debated between two choices. One was less practical but had a special deal going for it: free oil changes for three years. This sealed the decision for me. Later I realized that since I don't drive much, it was only $150 to $200 in savings. And in the end I was left with a less practical car.