At least locally pricing errors are always decided in favor of the customer. Of course you have to notice it but you're always entitled to the lowest advertised price on any item.
Yes, customers that notice it can have it corrected to the accurate, lower price. But the problem is that whenever there were "whoopsies", it's hard to just believe it was just a bug or well-intentioned mistake when there were never mistakes that would have resulted in a lower price.