The article explores why prices for the same products can vary between stores and how this price difference persists over time. By analyzing data from stores in Israel, the researchers found that even after considering differences in products, prices still vary. They also discovered that stores change their position in the price ranking, making it hard for consumers to consistently find the cheapest option. This means that price differences between stores don't go away and continue over time, as shown in a model by Varian from 1980.