The most expensive private jet in the world is the Boeing Business Jet 747-8i. This remarkable aircraft is a customized version of the Boeing 747-8, with a price tag ranging from $350 million to $500 million. The BBJ 747-8i offers an immense cabin space of over 4,800 square feet, which can be tailored to the owner's preferences, featuring luxurious lounges, bedrooms, dining areas, and even onboard offices.