“The price of a can of soda in a vending machine can now vary with the temperature outside.”

“The price of the headphones Google recommends may depend on how budget-conscious your web history shows you to be, one study found. 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.”