For example, your store might be competing for business using the headline price of eggs and making it up on milk and bread. In our city, Whole Foods was the cheapest non-warehouse place to buy eggs for a while. Anecdotally, it looks like one could save a relatively large % on various goods simply by going to a different store, which was not the case a few short years ago.
Relative pricing stability appears to have collapsed, shopping is more intellectually-intensive now.