8 . As Christmas approached, the price of turkey went wild. It didn’t rocket, as some might suggest. Nor did it crash. It just started waving. We live in the age of the variable prices. In the eyes of sellers, the right price—the one that will draw the most profit from consumers’ wallets—has become the focus of huge experiments. These sorts of price experiments have become a routine part of finding that right price.

It may come as a surprise that, in buying a pie, you might be participating in a carefully designed social-science experiment. But this is what online comparison shopping has brought. Simply put, the convenience to know the price of anything, anytime, anywhere, has given us, the consumers, so much power that sellers—in a desperate effort to regain the upper hand, or at least avoid extinction—are now staring back through the screen. They are trying to “comparison shopping” us.

They have enough means to do so: the huge data tracks you leave behind whenever you place something in your online shopping cart with top data scientists capable of turning the information into useful price strategies, and what one tech economist calls “the ability to experiment on a scale that’s unimaginable in the history of economics.”

In result, not coincidentally, normal pricing practices—an advertised discount off the “list price,” two for the price of one, or simply “everyday low prices” are giving way to far more crazy strategies.

“In the Internet era, I don’t think anyone could have predicted how complicated these strategies have become,” says Robert Dolan, a professor at Harvard. The price of a can of soda in a vending machine can now vary with the temperature outside. The price of the headphones may depend on how budget-conscious your web history shows you to be. The price may even be affected by the price of the mobile phone you use for item search. For shoppers, that means price—not the one offered to you right now, but the one offered to you 20 minutes from now, or the one offered to me, or to your neighbor—may become an increasingly unknowable thing. “There used to be one price for something,” Dolan notes. Now the true price of pumpkin-pie spice is subject to a level of uncertainty.