16. 1934 Mercedes 540K Roadster
The 540K was the ultimate pre-war Mercedes luxury convertible. Powered by a supercharged straight-eight engine, it was extremely expensive. Only a dozen or so were built.

Not many have been preserved because of the overall rarity. The ones that were sold for astonishing prices due to the car’s history. The last one fetched almost $12 million on auction a few years back (via Sports Car Market).