For current production models, the Ferrari FFX will set you back U.S. $1.7 million--and you have to be an executive-level Ferrari customer in order to even be *considered* for ownership. There is a long list of pre-requisites you have to meet to be put on the list for the car. And being next-generation concept cars, they're never going to see the street--they'll be kept at Maranello, and the owners will have to fly to Italy to drive them.
The current base MSRP for the 2007 Rolls Royce Phantom is $328,750. Less than a third the Ferrari's cost--and less than a third of the screaming performance the Ferrari offers. (Though, admittedly, three times as luxurious as any of Ferrari's models past or present.)
There are Ferraris that fetch over $2.1 million at auctions around the world--but they are incredibly rare #1 show cars of eras past, and their pricing can't be governed by the modern retail market.
So overall, I'd say that Ferrari produces the costliest and most exclusive cars.