That’s happening more frequently. I’ve used that mismatch twice to my advantage at a certain Big Box store.
For example, the price on a fancy light bulb was $8.98 if you believed the shelf, and $29.xx if you believed the bar code scanner. I used my cell phone to snap a picture of the publicly stated price. Then talked to management. Showed them the photo. And said, “This is what I saw with my own two eyeballs. Therefore, this is the price you advertised. The price you must honor. I don’t read bar code.”
I know, I know, they SAY that the bar code price is the real price. But since when did THEIR incompetence become MY problem?
In my case the product had a sale price tag on the shelf that had expired but someone neglected to remove the tag. So the cashier gave it to me for the sale price anyway. No argument from her, she was very polite and apologetic.