Costco's website currently features a $320,000 diamond engagement ring as well as a $2,500 espresso machine. "A Porsche dealer in Seattle put their cars on the floor of a Costco, and they sold out ...

10-karat diamonds,” James said. While most of Costco’s members are “average-income earners,” James noted that “affluent members with two times the average income” allow the business to ...

Though it's better known for bulk deals for budget-savvy members, Costco also sells more expensive items geared toward wealthier buyers.

"Since the beginning, we’ve always known we could move anything in volume if the quality was good and the price was great—Rolex watches, Dom Perignon, 10-karat diamonds," James said.