What is the most expensive car in the world?

The Bugatti Veyron was one of the most expensive cars in the world during its production, with prices ranging from \$1.5 million for base models to over \$3 million for special editions like the Super Sport. While newer cars may have surpassed it, this question appears to reference the Veyron's record during its production era. The Ferrari Enzo, SSC Ultimate Aero, and Lamborghini Reventón were all expensive but generally less costly than the Veyron.