How does the ending of "The Necklace" relate to real life?

The final line of the story is as follows: 

"Oh, my poor Mathilde! Why, my necklace was paste! It was worth at most only five hundred francs!"

 

This relates to real life because Mathilde acted throughout the story on what she thought to be the case, or what she thought should be the case, as people so often do. She mistook appearance for reality. She did this with herself, mistaking youth and beauty for some innate quality, she did this with society, mistaking the pretty show for what is important, and she did this with the necklace. That's why this story is a classic; the irony is deep and true.