Characteristics of the US Economy
Supply and Demand: Consumers want their iPhones
As new iPhones come out, the demand is high, so the price is high. When another iPhone or cheaper product of equivalent value, like the Samsung Galaxy, comes out, then the old models have a huge supply, so the price gets dropped really low.
Scarcity: Water on this planet
On the Planet Earth, the resource of water is limited. We use so much of it in our bodies, for cleaning wounds, and for other tasks except drinking. The water that is "clean" and can be consumed is even more scarce than the water on the entire planet. That is why when this item is scarce, it takes a lot of money to buy bottles of water.
Choice: Pepsi or Coke
When given two options, people have to make a choice to see which is the better option. A large debate is over people should choose Pepsi or Coca-Cola, although they are basically the same thing. When making a choice, you have to decide which is the better outcome, and which is not.