Electronic shelf labels mean grocery stores can now change their prices anytime they want, in seconds

Perusing the grocery aisle in the Westside Market on 23rd Street in Manhattan, you might not even notice the screens. They look just like paper price labels and, alongside a bar code, use a handwriting-style font we’ve come to associate with a certain merchant folksiness. They’re not particularly bright or showy. The only clues that they’re not ordinary sticky shelf labels are a barely distinguishable light bulb and, on some, a small QR code.

These are electronic shelf labels, chip-enabled...