In a lot of places in the US, the lower of the shelf price and the scanner price is by law the most they can demand, at least for retail sales to consumers. Attempts to stop the customer from leaving after having paid the legally appropriate amount would be criminal acts by the store, no?
I did call it a theoretical option and not a practical option. Although they might be a little more sympathetic to someone who is white, in a business suit, has a photo of the shelf price on their phone, can confirm that a surveillance camera captured them paying the shelf price, and is lucky enough to either get a cop who knows about the local price accuracy law or can point the cop to a visible posted sign about the law in the store.
