Would you return it, pay the difference or keep it?

“I bought this gorgeous dresser that was only $20 at a local thrift store!
I went back there yesterday when the same woman that cashed me out told me that the dresser had been priced wrong.
It was supposed to be $200 and she asked me to either pay the full amount or return it by the end of the week.
I told her that wasn’t fair, but she says if I don’t she’ll call the police.”
What do you think?