I remember back when I worked one my boss explained that our store made about 4 cents per dollar on most food items.

And for a lot of them that were easily damaged, and thereby we lost a lot in transit due to shit warehouse workers, we basically stocked them at a loss just to keep the vendor happy and our customers coming in to buy other things.

Grocery stores have a lot of faults but their markup is usually one of the fairest in the business.