Massachusetts has a quite prominent law against this. "When buying groceries—food and non-alcoholic beverages, pet food or supplies, disposable paper or plastic products, soap, household cleaners, laundry products, or light bulbs—you must be charged the lowest displayed price, whether on the sticker, scanner, website, or app. If the lowest price you saw for an item is $10 or less, and that lowest price is not what yo…
Yup. My local Star Market was pretty bad about this, so I started paying close attention to prices on the shelf and at the register. Pretty soon I was taking home free items every shopping trip. (I also reported them to Inspectional Services when aisle scanners were broken or prices were particularly egregiously missing or wrong.) Some of the cashiers had to have it explained to them with much pointing to the sign th…
It's both true. Given that a typical store can have thousands of SKUs displayed, mistakes will _always_ happen once in a while. A forgotten price tag, an incorrect sale price, etc.
But at the same time, stores are more than capable of having a system to _fix_ these issues as soon as they are detected. It doesn't even take much, just a way for a cashier to flag an inconsistent price for someone at the back office.