How Much Can We Charge You?

The next frontier of American commerce is an algorithm that knows exactly how badly you need something, and exactly how much more you might pay for it.

A few months ago, hundreds of people participated in a grocery-pricing experiment that I think deserves more attention than it received.

They opened Instacart, looked at products from the same stores, and sometimes saw different prices for the same items. Instacart said the retailers involved were conducting randomized price tests to learn how customers …