We do so only when we can draw interest on our money. The end result must exceed what we place in the bank. A second analogy is that of farming. No farmer plants an ear of corn to get another ear of corn. The harvest must always exceed the value of the seeds planted.
Buyers operate under the same philosophy.
They will not ordinarily part with their money to get what equals their money. Every sale takes place only when the customer thinks he's getting a bargain. There are, of course, degrees of bargains. That is the meaning of comparison shopping. The principle of three should be the natural outgrowth of putting together a selling strategy that must by necessity grow out of probing and qualifying.