How much is that Tibetan doggy in the window?

The latest "it dog" is no tiny purse filler, it's the Tibetan mastiff.

The dogs are so popular among China's elite that a perfect specimen can sell for over $500,000. The large dogs were domesticated in the mountains of Tibet 6,000 years ago and are considered to be the oldest, biggest and fiercest domestic dog.

The mastiff may not only be the most expensive dog in the world, but also among the rarest, with only 100 pure-bred animals believed to exist.