I've never worked at a retail/food service place where I was personally able to do a price override. They were both very automated, and pretty much every privilege was held solely by the manager. Were I in this situation, however, I would alert my manager and have him deal with it, most likely by admitting wrong and correcting the problem, but if necessary deal with being berated.
I think there are a few things to keep in mind here. One, and it felt absurd hearing the guys talk about it as if they would take on management in correcting the erroneous price, I think we need to have some perspective. It's not as if this was a fraudulent company draining him for years, or a price being significantly more than advertised. It was 50 cents more. For a pack of 12 cookies. From SUBWAY. I'm not saying it's good, but I'm also saying it's not that big of a deal. I also want to note that when I worked in food service, people would regularly get mad at the posted price because they never even bothered to look before they ordered. So it was automatically my fault things were overpriced. Alright. Also worth noting none of those people were ever under the age of 40, which points to generational perspectives.
I'm rambling. It's late. Ultimately my point is this: is it wrong that the posted price was more than advertised? Yes. Is it wrong that they didn't seem to take the man's gripes seriously? Yes. But also we're ultimately watching an old man yell at some kid getting paid minimum wage (that, based on what Kevin was saying, was basically just trying to keep his job) over a 50 cent discrepancy. That's absurd.