Every franchise has the right to set pricing, usually within limits set by the corporation. Every store has different costs (rent, labor, fees and taxes) and must price their goods and services accordingly.
If you bother to read the fine print, you will see that advertisements always state that pricing is good only at participating locations. Your Food Lion ad tells you which stores participate. If you tried to use that ad at a Food Lion not listed, they would tell you, politely, to go pound sand.