I'm going to let you in on a secret. As much as I love economics, it was my worst subject in college. As in I got a C+ in my International Finance course after help from a tutor and what I suspect was a sympathetic professor. Some of this can be attributed to having different interests then but the rest has to do with my stubborn refusal to accept universal truths. While most economists study outliers, the discipline at the undergrad level is usually taught in a very black and white manner and behavioral economics gets little attention. This is why I am always happy to read articles that take into account human (often irrational) behavior.
I spent much of my flight to Philly catching up the stack of New Yorkers that has been taunting me for the past month and was thrilled to find this article from the Financial Page from the January 2, 2012 issue. The concept of layaway is minimally exciting to me but I was intrigued by Richard Thaler's concept of "mental accounting". While cash is cash, many people have very specific ways of categorizing their cash into buckets. This is why layaway is appealing to some consumers. Even though there are transaction costs associated with layaway purchases, consumers have a more concrete way to tie their savings to a goal.
Perception, not charts, is what drives most people's decisions. Unfortunately, a lot of econ classes leave out the piece about how people perceive their financial options and focus on what they are supposed to do. Of course, if everyone did what they are "supposed" to do, financial crises probably would cease to exist as would economics as a discipline.