When the narrator ordered only mutton chops, the lady is incredulous, and she criticizes him for ordering such a filling dish. She claims she never ate anything as heavy as chops, as it would overload her stomach. For his part, the narrator only orders the mutton because it is the cheapest dish on the menu. Because he is a struggling writer at the time, the narrator knows he can't indulge himself if he wants to be able to afford the bill.
When his dish arrives, the lady once again lectures the narrator about eating such a "heavy luncheon." In truth, the narrator only orders one mutton chop. For her part, despite professing she never eats a large luncheon, the lady has salmon, caviar, asparagus, a peach, ice-cream, and coffee for her meal.
To add insult to injury, just as she chooses a ripe peach from the basket the waiter brings over, the lady lectures the narrator about eating meat. Seemingly oblivious to the expense the narrator incurs on her behalf, the lady again lectures her host as they leave the restaurant. The narrator knows he will be penniless for the month, but tells us his revenge came later. Years after the luncheon, the narrator discovers the lady now weighs twenty-one stone (almost three-hundred pounds).