After ten years of sales, 500 million Amazon smart devices have found their way into homes around the world. But the company is losing billions of dollars on the devices. WSJ’s Dana Mattioli discovered an accounting tool that’s kept the huge losses under wraps. Further Reading: -Alexa Is in Millions of Households—and Amazon Is Losing Billions Further Listening: -Amazon's Secret Operation to Gather Intel on Rivals -What Is Amazon's Secret 'Project Nessie'? Learn more about your ad choices. Visit megaphone.fm/adchoices