Why is Amazon willing to sell its Kindles so cheaply that they make no profit—or even lose money? Easy: Kindle owners end up spending more money on Amazon, Time reports. New research from the Consumer Intelligent Research Partners finds that Amazon members who don't own a Kindle spend $790 on the site each year, while Kindle owners spend $443 more, for a total of $1,233 per year. Says CIRP's co-founder, "Another way to look at Kindle Fire and Kindle e-Reader is as a portal to Amazon.com." Want to get a little of that back? Over at Slate, Matt Yglesias has figured out a loophole involving a fake baby. (More Amazon.com stories.)