What is the most expensive car in the world?

Can you shed some light on the topic of the most expensive car in the world? I'm curious to know which automotive masterpiece holds that prestigious title, and what makes it so incredibly valuable. Are we talking about a rare collector's item, a custom-built one-of-a-kind masterpiece, or perhaps a technologically advanced hypercar? What features and specifications set it apart from the rest, and how much does it cost? I'm eager to learn more about this automotive masterpiece.