Of course, the most obvious thing about this story is the ridiculous irony. Mme Loisel attempts to live beyond her means. She reaches too high to pretend to be something she is not. Her pride and vanity lead to her ruin. Her husband wishes to please her, but she treats him with nothing but contempt. He gives her what she wants, even at sacrifice to himself, yet she shows no gratitude toward him, no thanks, only demands for more. Perhaps this is why she is punished. She believes herself above her class, like she was born to be in a rank higher than hers. This is what happened to Anna Anderson--the woman who claimed she was the lost Grand Duchess Anastasia. Anna Anderson was actually a Polish peasant who always believed herself meant to be royalty. Anna Anderson's memory is now in infamy for an impostor who claimed to be a lost princess. History does not look kindly upon her.
Mme Loisel becomes the woman she was always supposed to be--strong, rough, sturdy, ruined hands. She still dreams of the old days, but she has become accustomed to a life of hard work and labor. Yet had she not tried so hard to pretend to be something she was not, she would still have a moderately comfortable life. Yes, she would still be dissatisfied, but she would not suffer. Maybe she is happier accepting her lot and working hard toward a goal because she must, rather than moping around and lamenting the fact that she did not have a dowry when it was time for her to marry.
The bitter irony is too much to bear. Mme Loisel could have told Mme Forestier the truth, and Mme Loisel would never have had to pay back such a ridiculous sum. Mme Forestier ends up the richer in all aspects--she has the diamond necklace replacing her fake one, she still looks young and beautiful, and she is still above Mme Loisel in social stratification. It's a sacrifice Mathilde makes--one night of joy and beauty for a lifetime of servitude and poverty. Ten years of hard work is the price she pays for her one night of high society and class, living the life she thinks she was supposed to have. But she is punished for her vanity.
It's a short, simple story, but it makes you wonder what Maupassant's message was. Don't try to reach beyond your means? Don't be proud? Appreciate what you have? Mathilde suffers much more in the beginning of the story than the end, even if she does have a housemaid. But once she gets down to work, maybe she is happier. Accept things for what they are and be happy about it? Ah well, I'll enjoy the irony in it like in "The Story of an Hour."