The 26-year-old star auctioned off her custom Prada dress after wearing it on the red carpet to the Costume Institute Gala held at New York's Metropolitan Museum of Art earlier this month, reported Contactmusic.
After being listed for sale two days later, the designer frock went to the highest bidder when the auction closed on May 19 with a total of 35 bidders.
The proceeds of the dress will go to Oxfam America, an organisation which aims to eradicate poverty.