Image credit: Stuart Hughes

Expensive, high-end smartphones or smartphone cases are nothing new - Vertu's got a $9,600 Android phone and London Loutus made a $300,000-plus iPhone case with crystals. But Stuart Hughes, a longtime designer of aftermarket electronics, has topped them all with a $15 million iPhone 5, believed to be the most expensive smartphone ever made.

The phone has a solid-gold chassis that Hughes crafted by hand. But the real cost comes from the most expensive home button in the world.

That home button is made of a single, deep-cut, black diamond that weighs 26 carats. The diamond is said to be worth $14.5 million.

And the diamonds don't end there. There are 600 white, flawless diamonds located within the Apple logo on the back and on the edges.

The English designer and jeweler has made gold Apple products before - his Solid Gold iPhone costs $33,678 ( £21,995) and the iPad Supreme Fire Edition costs $168,424 (£109,995) - but with this one, "it's all about the rarity and value of the deep-cut, black diamond," he told ABC News.

The phone isn't available to the general public - not that most of the world's population could afford it. Hughes spent nine weeks creating the phone specifically for a Hong Kong businessman whom Hughes will only refer to as "Joe." Joe had owned the black diamond for awhile and decided he wanted to place it on an iPhone after buying other, "cheaper" items from Hughes in the past.

However, Hughes isn't worried that the world's most expensive smartphone might soon become outdated when Apple puts out a new iPhone (possibly this summer). He is confident other customers will want that next iPhone - whether it be called the iPhone 5S or 6 - to be adorned with diamonds and gold, too.

"I have been commissioned to do all of the iPhones from when the 3G version first came out," said Hughes, who added he gets most of his business through referrals.

And no, you can't purchase any of Hughes' blinged-out iPhones with bitcoins.