In “A&P,” the protagonist Sammy appears to be from the working class while a female customer whom he dubs “Queenie” belongs to the upper middle class. Updike illustrates their characters’ socioeconomic differences in the short story’s opening lines:

In walks these three girls in nothing but bathing suits. I'm in the third check-out slot, with my back to the door, so I don't see them until they're over by the bread.

Right away, Updike sets up a clear contrast between Queenie and Sammy. Leading around two friends on a leisurely summer afternoon, Queenie has time and money to purchase snacks at a grocery store. Sammy, on the other hand, is busy at his job as a cashier in a checkout aisle. His companions are hourly employees like him. Sammy is a service worker resigned to abuse by customers. When distracted by the girls’ appearance, for example, he is scolded by a

customer [who] starts giving me hell. She's one of these cash-register-watchers, a witch about fifty with rouge on her cheekbones and no eyebrows, and I know it made her day to trip me up.

Sammy also seems accustomed to this dismal setting in the middle of a town “five miles from a beach” with a clientele of housewives “with six children and varicose veins mapping their legs.” Updike conveys the mundane, lower-class socioeconomic flavor of Sammy’s community with the description

if you stand at our front doors you can see two banks and the Congregational church and the newspaper store and three real-estate offices and about twenty-seven old freeloaders tearing up Central Street because the sewer broke again. It's not as if we're on the Cape; we're north of Boston and there's people in this town haven't seen the ocean for twenty years.

The grocery store where Sammy is trapped behind the counter is so quiet and empty that he has “nothing much to do except lean on the register and wait for the girls to show up again.”

Queen seem completely out of place in this setting with her fashionable bathing suit, white shoulders, “long white prima donna legs,” and bare feet. In fact, she seems quite used to wearing shoes, perhaps nice ones with heels. Sammy notices that when she walks, she comes

down a little hard on her heels, as if she didn't walk in her bare feet that much, putting down her heels and then letting the weight move along to her toes as if she was testing the floor with every step, putting a little deliberate extra action into it.

Queenie’s appearance is striking and seemingly more refined than Sammy is used to seeing at the grocery store. Striding with an air of confidence and entitlement, she shows off her long neck,

oaky hair that the sun and salt had bleached, done up in a bun that was unraveling, and a kind of prim face.

Updike demonstrates the stark difference in economic and social class between Queenie and Sammy through Queenie’s purchase: the fancy snack, “Kingfish Fancy Herring Snacks in Pure Sour Cream” which costs 49¢ (worth $4.28 in 2021). She casually pulls out a dollar bill out of her bathing suit to pay for it.

"My mother asked me to pick up a jar of herring snacks." Her voice kind of startled me, the way voices do when you see the people first, coming out so flat and dumb yet kind of tony, too, the way it ticked over "pick up" and "snacks." All of a sudden I slid right down her voice into her living room. Her father and the other men were standing around in ice-cream coats and bow ties and the women were in sandals picking up herring snacks on toothpicks off a big plate and they were all holding drinks the color of water with olives and sprigs of mint in them.

Even the way she speaks emphasizes her higher economic and social class. Her “tony” voice takes Sammy into her home where her parents entertain well-dressed guests with hors d'oeuvres and martinis served by help. In contrast, Sammy notes that his parents would serve their guests lemonade and

if it's a real racy affair Schlitz in tall glasses with "They'll Do It Every Time" cartoons stenciled on.

Instead of garnished cocktails, Sammy’s family can offer only beer in cheap glasses decorated by a popular and sardonic comic strip/gag panel.

Finally, Queenie’s disdain for Sammy and his working-class colleagues illustrates her higher socio-economic status. When admonished for wearing her bathing suit in the store, she declares,

"We are decent," Queenie says suddenly, her lower lip pushing, getting sore now that she remembers her place, a place from which the crowd that runs the A & P must look pretty crummy.

Although Sammy quits his job in a show solidarity, he admits that he does not really want to disappoint his parents, especially his mother who ironed his work shirt the previous evening. Most importantly, he learns that he is easily replaced as a worker and that committing future gestures of idealism and principle will not be easy for someone of his class. He sadly realizes “how hard the world was going to be to me hereafter.”