Dead serious saw a person try this in Target last year:
Checker rings up a PS4.
Customer looks at the price and goes "oh no, that price is wrong, it said $150"
Checker runs it again, still $400 or w/e they were at the time.
Customer continues arguing.
Checker asks for a price check, comes back $400.
Customer says that it was on a shelf that had a $150 price tag.
Checker says that another customer may have left it there, or it was misplaced, etc.
Customer gets belligerent, starts talking about how they should honor their prices and it's not their fault it was on that shelf.
Checker says there's nothing they can do.
Customer says "Fine, I'll just take my business elsewhere!" and storms out.
I could never work in customer service. Respect those folks so much.