Apple's results send shares tumbling

It's hard to imagine that the second-best quarterly profit ever made by a U.S. company wasn't good enough for investors.

But Apple isn't an ordinary company. And signs that the tech giant's unbelievable growth might be slowing is enough for investors to flee the stock.

One of the main worries is that consumers are buying cheaper Apple products instead of the high-end ones. Buy an iPad mini instead of the full-size iPad and you could save over a hundred dollars - but that's a hundred dollars less for Apple.

However, a look at the smartphone sector tells a different story – for now, at least.  For an idea of just how much revenue Apple generates per device, let's compare it to Nokia, which reported results a day later.

Nokia sold 86 million phones over the last 3 months. Apple sold almost 48 million iPhones.

But Apple pulled in over $30 billion in revenue from those phones. Nokia's sales were just over $5 billion - a fraction of Apple's, despite selling millions more devices.

Apple's ability to sell so many phones at such a high cost is an incredible (and enviable) achievement.

But investors don't believe it's one the company can sustain.