Butter – 7 francs.
This went on for a while until eventually one of the lady’s customers pointed to the sign and said, “Madame, you cannot keep your prices so low for long. These big companies can use their buying power to sell products cheaper, but a little store like yours can never compete.”
In response, the old lady bent forward conspiratorially and muttered, “Monsieur, I don’t even sell butter.”