Rolls also is following up on a record year, in this case reporting a 33 percent rise for the first half of 2014. It sold about 1,968 of its various models through the end of June. Rolls has traditionally had a more posh image than Bentley, and its products, such as the "base" Ghost line, which begins at $250,000, and the big Phantom, starting at around $400,000.
Bentley and Rolls are both looking at ways to grab even more buyers. The VW subsidiary will bring an all-new premium SUV to market about a year from now, and Rolls, which is owned by Germany's BMW, may follow that path, as well.
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The long-running debate is whether there is – or should be – a limit to demand. So far, analysts like Phillippi believe, the most prestigious carmakers have been able to build sales without damaging their brand image. In part, that's because they've grown their global footprints by targeting promising new markets like China. Indeed, the People's Republic has already become the largest outlet for some luxury marques and may soon pass the U.S. in sales of the most exclusive models.
That said, some manufacturers remain concerned about the potential to dilute their brands. Ferrari, for one, planned to scale back production to around 7,000 vehicles annually, off from more than 7,300 in 2012, which will likely mean even higher prices.
"The exclusivity of Ferrari is fundamental for the value of our products," the maker's chairman Luca di Montezemolo told journalists last year. "We don't sell a normal product. We sell a dream."
—By Paul A. Eisenstein, NBC News