There's a joke about economists, and it goes a little something like this.
Two economists are walking through a forest when they come across a giant pile of bear poop. The first economist says to the second, "I'll give you $100 if you pick up some of that bear poop and taste it." the second economist cringes, but does as instructed. The first economist grinning, hands him $100. They continue walking for a while and eventually come upon a second pile of bear poop. This time the second economist says to the first, "I'll give you $100 if you eat that bear poop." The first economist dips his finger in, licks it, and swipes the $100 bill back.
They've not gone 10 yards before the first economist gets confused. "What just happened?" he says. "Because it seems to me like we both just ate bear poop for free."
"Not at all," replies the second economist. "We increased the GDP of the forest by $200."