Costco sold someone a $400,000 diamond ring - CNBC

- Costco got a sales boost during its latest quarter thanks to one customer purchasing a ring there for more than $400,000. - The warehouse retailer sells a lot of things besides just groceries in bulk. Did you know you can buy diamond rings at Costco? And expensive ones, at that. The warehouse retailer said during its latest quarter ended May 12 it got a sales boost thanks to a customer purchasing one of its rings for more than $400,000. It didn't say which ring, exactly, but a search on Costco's website reveals only one ring priced in the $400,000 range: A "Round Brilliant 10.03 carat VS1...