The necklace might be considered a symbol of wealth, of vanity, of deception, of illusion, of false values, high society, an illusion to Cinderella, or something else. The story is bitterly ironic. Not only does Mathilde suffer from paying a fortune for a necklace that is made of fake jewels, but her poor husband, who was only trying to make her happy, is dragged into the pit of despair along with her. Irony is often, if not always, like a bad joke. It is like a joke that would be funny if only it were not so painful. It would take a very cruel reader to laugh at Monsieur and Madame Loisel for what happened to them. That is why the story is ironic and not funny. They work and slave for ten years to pay for a replacement necklace that was only worth about five hundred francs, something like a hundred dollars in American money at the time. Not only that, but Mathilde loses her beauty, grace, charm, and even her dreams during that terrible time.
It is true that she is punished for her vanity, but she isn't much different from the rest of us. It is hard to laugh at her when it is so easy to understand her. The rich people she reads about, as well as her friend Madame Forestier, make her feel envious. She knows she is as good as they are, if not better. She knows she is prettier and sexier and more attractive in many ways than her friend Madame Forestier and than all of the women who will be going to the Minister's Ball. But aren't we all a little envious of people who have more than we do?
Goe, and catche a falling starre,
Get with child a mandrake roote,
Tell me, where all past yeares are,
Or who cleft the Divels foot,
Teach me to heare Mermaides singing,
Or to keep off envies stinging,
Serves to advance an honest minde.
This seems to be how Maupassant makes his tale ironic. We don't want to see Mathilde suffer and lose her beauty. We don't want to see her husband spending the whole day working at his job and then trying to make a few extra sous doing copy work at home by candlelight. And most of us, unfortunately, know what it feels like to be in debt, robbing Peter to pay Paul, borrowing money to pay back borrowed money. It is torture. If the situation gets bad enough it can keep people awake nights with pounding hearts, when they should be resting, storing up physical and mental energy for the battle for survival that will begin again tomorrow. It is ironic that the necklace wouldn't have really been worth a fortune even if it had been made of real diamonds. Maupassant seems to be saying that life itself is of vastly more value than mere objects.
Do you not see what feigned prices are set upon little stones and rarities? and what works of ostentation are undertaken, because there might seem to be some use of great riches?
Francis Bacon, “On Riches”