Machines meeting the MacBook Air’s specification can be built cheaply enough; Apple’s managing it, and Intel’s price estimates probably aren’t too far off. But they require a different approach to PC building. For example, Apple’s laptops use custom-sized lithium polymer batteries. These allow Apple to make the battery exactly fit the space available, maximizing battery life and minimizing space, but there’s a downside of sorts: Apple can’t use standard battery modules. Similarly, the MacBook Air uses a highly integrated motherboard, with almost all functionality built-in. This makes the board smaller and cheaper to produce, but it means Apple doesn’t offer a wide range of processors, GPUs, WiFi adaptors, etc.
Apple has changed the way it builds systems. The company has boasted about it, in fact; when Steve Jobs talked about the unibody construction process used since late 2008, he was, in effect, telling the PC world “we’ve made this kind of investment—catch us if you can” (and so far, the PC companies can’t). In 2010 he made the challenge again when he claimed that “We think all notebooks will look like these one day.”
Apple didn’t achieve this overnight; it was the result of close cooperation with its supply chain (changes driven by Apple’s new CEO, Tim Cook), greater vertical integration, a deliberate policy of not shipping a million different models, and an absolute willingness to offer premium products at premium prices. That’s why Apple, and only Apple, can now make the MacBook Air and sell it for $999.