Price: $12.8 Million*

Ok, technically the Rolls-Royce Sweptail claimed the title "world's most expensive car" in 2017. Problem is, Rolls-Royce didn't officially confirm that number, meaning the next car on our list takes home the title. But at an estimated $12.8 million, the one-off Sweptail outpriced the next-most-expensive vehicle by a jaw-dropping $5 million (if reports are true). The Rolls-Royce Sweptail took more than four years to develop before its debut at the 2017 Concorso d'Eleganza Villa d'Este.