In The Necklace (the short story by Guy De Maupassant) the necklace itself could be taken as a metaphor for the illusion that goodness and integrity,respect and status in society rely upon wealth and material possessions.
A couple risk all that they have, which may not be much but at least means respect, reputation and earning their own living mostly free from debt. This story could say a lot about the credit situation many of us are in now - many countries are chained in public borrowing and many households are fighting and working every hour to repay material possessions or houses they couldn't really afford.
Maybe those things look like a sham to us too,now, as parents work longer and longer hours not spending time with their families trying to pay down debts.
Appearances are deceptive 'all that glisters is not gold.'
The couple in the story risked everything to pay for something that wasn't really worth it.
The simile in "The Necklace" was answered recently. You can find it at the link below.