Imagine a wristwatch that costs $815,000. Imagine a wristwatch that costs $815,000 and contains no diamonds or precious jewels. Imagine a wristwatch that costs $815,000, contains no diamonds, but in some alternate universe of watch geekery may even be considered, yes, a bargain.

The watch is question is the Greubel Forsey Quadruple Tourbillon, of which there are four models.

The Quadruple Tourbillon is not only the signature watch of Greubel Forsey, one of the world’s most exclusive watchmakers, based in La Chaux-de-Fonds, Switzerland, it is also one of the rarest current-production timepieces. The tiny company, founded in 2004, produces only five or six Quadruple Tourbillons a year.

Even so, how does a single watch command the price of about 100 Rolex Submariners, or maybe 10,000 Casio G-Shocks (not to mention a five-bedroom house in certain New Jersey suburbs).

I recently spoke to the company co-founder Stephen Forsey to find out why the watch costs so much. The answer begins with its engineering.