I would like to think incompetence as well, but when the problem is this widespread, IMHO it does point to a corporate issue...even if that's simply leaving too many incompetent managers in charge. IMHO if you're the manager and the part-time teenager didn't finish updating all the shelf pricing, then it's on you to finish before going home. But today too many people just don't give a damn.

My first job was in retail as well, going back to the days before scanners when every item item was ticketed individually. When something goes on sale you ticket it again, then tear off the sale price stub when the sale ends. Repeat as needed. Maybe that could be a suitable punishment, too? Force stores to abandon shelf pricing for a period of time until it hurts enough that they get their act in order?

Where I live the rule is simple, and all stores adopted it.

If something is mislabeled you get (one of) free, and all the rest at the lower price. (And you see a worker skurry off to fix it immediately.)

And here's a shock, mislabelling is vanishingly rare... seems it can be done if desired...