5. A Foldable Couch
A German student came home with a $215 foldable couch she had bought at a flea market, only to have a painting fall from out from its crease.
Source: Revolvy
The painting was actually rare, having been created between 1605 and 1620 by an unknown artist. It depicted Italian master Carlo Saraceni. Despite the unknown artist, it eventually auctioned for $27,630!