Kim Kardashian's ex-husband made a $370,000 profit from her engagement ring.

Boston Celtics star Kris Humphries auctioned off the reality TV star's 20-carat diamond ring for $620,000 at Christie's auction house in New York City on Tuesday (15.10.13), and jewellery designer Lorraine Schwartz is reportedly furious as the piece, which features a 16.21-carat centre diamond between two 1.8-carat diamonds, is actually worth $2 million.

A source told gossip website that Lorraine was hoping the basketball star would return the ring to her for a refund as she gave him a ''huge discount'' and sold it to him for $250,000 in 2011 because Kim is her friend.

The insider said: ''He could have returned [the] ring, very low-key and would have had his money returned. Lorraine Schwartz took a huge loss on it, and would have appreciated first offer of refusal before it was put up for auction.''

Meanwhile, Kim, 32, doesn't care that Kris, 28, has profited from the sale of her ring.

A source close to the 'Keeping Up with the Kardashians' star - who dumped Kris after just 72 days of marriage in October 2011 and now has a four-month-old daughter, North West, with her boyfriend Kanye West - said: ''Kim only gave [it] back after she got [pregnant] with Kanye's baby and boasted during divorce proceedings, 'Kris can have the ring back because Kanye is going to give me a flawless diamond engagement ring that makes my previous ring look like [a] Cracker Jack prize!'''