Answer by Harold Citron:
Rule number 1: There's no Free Lunch (Thank's Professor Russ Roberts).
The understanding here is that everything in life, and I mean everything, bears a cost. The cost may not be in the form of actual dollars and cents, but anything that creates utility requires input from someone and somewhere.
Rule number 2: "It's like your Rock Star Mick Jagger once say: 'I Can't Get No Satisfaction' – That is economics!" (Thanks Professor Ching Hsieh).
The understanding here is that life is filled with constraints. Prioritizing these constraints forces people to prioritize their decisions about what actions and physical objects, provide them with the most utility vs. the cost (see rule #1) they must pay.
Just because some decisions in life seem poorly made, or irrational, means that both costs and utilization change over time, including very short periods of time vs. long periods of time.
Akira Morikawa 