Freakonomics

Economics is, at root, the study of incentives: how people get what they want, or need, especially when other people want or need the same thing.

These budding drug lords bumped up against an immutable law of labor: when there are a lot of people willing and able to do a job, that job generally doesn’t pay well. This is one of four meaningful factors that determine a wage. The others are the specialized skills a job requires, the unpleasantness of a job, and the demand for services that the job fulfills.