Parable: Gross domestic product

To my grandfather in the village for the summer came grown-up grandson. Competent already gone, but the curiosity its not lost:
- Grandpa, why do not you like money? Money - it's power!
- What they love? Here's the situation, and you are competent, explain it to me: when we had no money, and I needed fat, I took a bag of potatoes that he grew and walked with her to my neighbor who breeds pigs. We sat down at the table and talked for a long time mentally. It was not just the exchange of ideas, and the event. If a neighbor needed a potato, then he walked over to me and brought me instead a piece of that awesome bacon. Now, to have money, I sold not two, but four bags of potatoes. This money is just enough to buy two pieces of bacon. I suspect that the neighbor is now the situation is the same, since a long time he comes to visit. And now you tell me - that my neighbor has benefited from the fact that he had sold the potatoes and bacon for money?
- Grandpa! It's easy! Your two bags of potatoes and two of the neighbor's piece of bacon, which seemed to have disappeared after exchange your products for money, turned into a gross domestic product! laughed the young man.