Many customers stock up on those days. Most of us unfortunately do not know complexity of the food pricing. I firmly beilive that all of the food pricing could be much higher and more unreasonable. Only thing that effectively keeps natural barometer and the scale of the pricing equalized is supply and demand. Customer reaching for the item or hesitating to pick it up is a sure sign in what direction price is to go.
Merchant can predict from the previous experience how to price the item.
Dormant items throughout the year become high priced peak items during demand period. Good examples are turkeys, cranberries and Christmas cake during Noel Season. Customer is still the boss. If customer doesn t buy, merchant will be out of business. Every fluctuation in world economy will directly effect food pricing.