The wealth of the Sultan of Brunei is derived from the oil that is found inside the country's borders. According to an article by Business Spectator from Apr. 24, 2014, the Sultan's wealth is estimated to be $20 billion in total.
As of 2015, the Sultan reportedly resides in a palace that is fitted with 257 bathrooms and 1,788 rooms. The Sultan's palace is considered to be the second-largest palace in the world as of 2015, and is reported to have cost approximately $350 million to erect. The palace is also designed to include five swimming pools, a garage that fits 110 cars and a stable for 200 polo ponies.
An exact accounting of the cars that are in the Sultan's possession is unavailable, but reportedly a gold-plated Rolls Royce and the last Rolls-Royce Phantom VI are some of the rarities among his collection. Guinness World Records reports that the Sultan's car collection includes over 450 Ferraris and the largest collection of Koenigseggs numbering at 134. The royal family of Brunei accounted for nearly 50 percent of all Rolls-Royce purchases during the 1990s. Estimates place the total number of his automobile collection at approximately 7,000 cars and its worth at over $789 million.