In the beginning of the story, the tone of “The Necklace” is mocking and cynical. The narrator goes out of the way to tell the reader that Mathilde’s distaste for her apartment and possessions is unusual among women in her position:
All these things, which wouldn’t have even been noticed by another woman of her station, tortured her and infuriated her.
As the list of Mathilde’s irrational grievances piles up, the author is quick to let readers know that these things wouldn't even be noticed by most people—which means, of course, that the problem is Mathilde, not necessarily her circumstances. She seems ungrateful, even bratty, next to her husband, who is extremely happy with their simple domestic life. By highlighting this aspect, the tone of the story itself seems almost disdainful of materialistic people like Mathilde.
By the end, though, the tone of the story shifts to one of pity and sorrow, as the irony of the necklace’s worthlessness hits home. There is a lengthy description of the “horrible life of necessity” that the Loisels suffer as a result of Mathilde's mistakes. For his part, M. Loisel is subject to “all [...] physical deprivations and mental tortures” as he places himself in debt to unscrupulous moneylenders and usurers, works evenings for little money, and struggles to juggle his debts. Meanwhile, Mathilde herself is subject to strenuous, difficult physical labor without end, and she must abandon all previous material comforts. Whereas she used to daydream about wealth, she now must haggle with grocers and butchers. The sacrifice the Loisels make is so complete that the revelation that the necklace is counterfeit is crushing to both Mathilde and the reader, as it renders the Loisels' extensive suffering all but meaningless.
This painfully ironic end not only punishes Mathilde for her selfishness, it also elicits the reader’s sympathy. This sympathy complicates the story, allowing the reader to consider the role society has played in the Loisels' downfall. Their condition functions as an implicit critique of the greed around them, a greed reflected within Mathilde. By the end of the story, then, the reader is forced to grapple with the question of whether Mathilde is implicitly selfish and greedy, or a product of her environment. In a way, then, the story's tone returns to its initial cynicism—now, though, the cynicism isn't directed at Mathilde herself, but at the unfortunate societal circumstances that have led to her misfortune.