Apple could probably sell iPhones off the back of a truck parked under the freeway and still make a billion dollars. But its retail talents are far more impressive than that.

The iPhone maker is now the second-largest online retailer in the U.S. with sales topping $18 billion in 2013, according to new Internet Retailer data cited by The Wall Street Journal. Apple got an extra lift on this year’s list of top e-tailers, which for the first time included Apple’s hardware sales in its figures along with revenues from the App Store and iTunes. That bump was enough to lift Apple well past longtime number-two online seller Staples, not to mention other retail stalwarts such as Walmart, Costco, and Macy’s.

The iPhone maker is the second-largest online retailer in the U.S. with sales topping $18 billion in 2013.

Only Amazon sold more online last year than Apple, sitting alone at the top with nearly $68 billion in sales. As the Journal notes, that’s more than the 10 next-largest online retailers combined. But even next to Amazon, Apple’s success as a seller is remarkable. Amazon, remember, sells just about everything, while Apple mostly sells just digital goods and a few pieces of hardware. Also, retail isn’t Apple’s main business. Apple designs and builds computing devices.

In an alternate universe, Apple could have left the selling of its software and hardware in the hands of someone else, a way of focusing on making stuff. Instead, the company has opened a network of physical stores that do better business per square foot than any other chain in the U.S. And, as it turns out, they’re really good at selling stuff online, too.

Compare Apple to Walmart, the number four online seller after Staples with sales of $10.3 billion in 2013. The world’s largest retailer overall, Walmart has more than 2,000 employees in Silicon Valley working on cracking Amazon’s domination of e-commerce, and they’re getting somewhere — as the Journal also points out, Walmart’s online sales grew faster than Amazon’s last year. But Apple has pulled off a neatly choreographed trick that will be hard for any traditional retailer to match. Apple’s digital storefronts, iTunes and the App Store, make the company’s devices more desirable. And once customers buy those devices, they’re very much locked into those same stores to fill those devices with actual stuff.

In that context, Apple’s online hardware-selling business itself almost seems like an afterthought. The web version of the Apple Store is fine, but it’s nothing exceptional. But that could soon change, now that former Burberry CEO Angela Ahrendts has come on board to head up Apple’s retail operations, online and off. Apple, it turns out, is already one of the world’s best not just at making but selling stuff. Imagine what could happen if it actually started trying.