In one of our projects, Kristina Shampanier, Nina Mazar, and I examined whether our reaction to Free! is just a rational reaction to a low price (a very low price) or if it is an irrational overreaction to Free! We carried out a set of experiments in which we measured not only what people chose but also what they gave up in the process. By doing so we were able to show that Free! can tempt us so much that we are willing to forgo a really good deal for a mediocre one simply because it is Free! For now let’s skip the experiments and consider the following thought-experiment:
Consider how long you would be willing to stand in line for a free Ben & Jerry’s ice cream cone. Let’s assume that your answer is 20 minutes and that the cost of a Ben & Jerry’s ice cream cone is $1.45. Now answer this: would you be willing to stand in line for 20 minutes for $1.45 in cash? No way.
This is exactly what the experiments showed; when something is Free! we get excited and as a consequence we are willing to give up better deals — not to mention our time, money, etc.
For the original paper see this link.