Mercedez Benz SLK McLaren Roadster is worth about $560,000 and has a nice top speed of 206 mph. This car can reach 0-60 mph in just 3.8 seconds. Mercedez Benz SLK McLaren Roadster is the fastest car with automatic transmission in world. The Mercedes-Benz SLR McLaren Roadster unites the legend of the successful SLR racing models from the 1950s with the innovative technology of modern Formula 1.