Lamborghini's outrageous Veneno Roadster -- a $4.5 million supercar with no roof -- was unveiled in 2013. Just nine were built. Source: Automobili Lamborghini.

Italian supercar maker Lamborghini stunned crowds at the Geneva auto show in 2013 with its insane Veneno, a lightweight 740-horsepower hypercar -- and then again with the news that only three would be built at a price of about $4 million each.

A few months later, the company -- known for its audacious designs -- followed that up with something arguably even more radical: The Veneno Roadster, a car so extreme it didn't even come with a roof. Compared to the coupe, it was practically mass-produced: Lamborghini said it would build nine, at $4.5 million a pop.

All of the Venenos have long since been sold, but the cars still generate buzz two years later. Why did Lamborghini build the Veneno Roadster and coupe? And why would corporate parent Volkswagen Group (VWAGY -0.33%) sign off on such a project?

The Veneno Roadster: A Lamborghini, only even more so
To build the Veneno Roadster and coupe, Lamborghini started with its top-of-the-regular-line Aventador, a V12-powered monster that follows in the line of its hallowed forebears, the Murcielago, Diablo, and Countach.    

The Aventador isn't cheap, but at a starting price of around $400,000, it's a bargain compared to the Veneno Roadster. So what did the extra four-million-plus dollars get the nine lucky buyers who lined up for the open-top Veneno? 

The hot V12-powered Aventador tops Lamborghini's regular model range. At a starting price around $400,000, it might seem like a bargain next to the seven-figure Veneno Roadster. Source: Automobili Lamborghini.

It's possible to argue that the Veneno's pricing wasn't completely outrageous, but only barely. For starters, while the Aventador includes a lot of expensive carbon fiber in its construction, it's nothing like what Lamborghini did with the Veneno. 

Nearly the entire car was made from the expensive, superstrong material -- the monocoque chassis, all of the car's body panels, and many of its interior pieces were created using Lamborghini's special blend of carbon fiber. Even the seat-backs were made from the special composite.

To that superlight and superstrong foundation, Lamborghini added a tweaked version of its signature howling V12 engine, a 6.5-liter edition good for 740 horsepower. The upshot? A 3,285-pound howler that would do zero to 62 miles per hour in 2.9 seconds, with a top speed of 221 miles per hour.

That's impressive. But why sell just nine roadsters and three coupes? What was the business case for that?

Why Lamborghini built the Veneno Roadster
Lamborghini isn't saying, but it's a good guess that it built the Venenos for the same reason Fiat Chrysler's Dodge brand unleashed the 707-horsepower Hellcat versions of the Charger and Challenger last year: as a brand-building exercise.

Of course, it's a very different flavor of exercise, because Lamborghini is a very different brand. While Dodge CEO Tim Kuniskis was clear that FCA would build as many Hellcats as buyers wanted, Lamborghini ensured that most people would never have the chance to even see, much less drive, the Veneno Roadster and coupe.

$4.5 million, no roof: another view of the outrageous Lamborghini Veneno Roadster. Source: Automobili Lamborghini.

But that's part of the point: Lamborghini has always been the most exotic of the exotics, its cars rare and almost mysterious, with styling and capabilities that seem outrageous, even otherworldly.

Nowadays, of course, Lamborghini is part of the vast VW empire, and with 2,530 Lamborghinis sold in 2014, sales have been better than ever. But a car like the Veneno Roadster -- an insane car, at an insane price, with an insanely short production run -- adds to Lamborghini's legend, and makes the relatively affordable Aventador and Huracán models seem even more exotic and special.

Lamborghini will never build another Veneno Roadster, but...
Lamborghini won't be building any more Venenos. If you want one, you'll have to buy used. But if you can find an owner willing to sell, be prepared to pay dearly: A Veneno Roadster was offered for sale last fall, at a price of $7.4 million. 

The Venenos probably won't see a lot of highway miles. I expect that most will be traded among wealthy collectors for decades to come. But Lamborghini got a lot of attention from the Venenos -- and that makes it likely that there will be another, even more outrageous, limited-production Lambo in the not-too-distant future.