Not unrelated: The House of Saud is losing a lot of money on the Credit Suisse rescue/buyout.
A billion isn't worth losing sleep over here.
There's a reason why Forbes does not even rank royals' wealth. It's a futile journey trying to decipher what belongs to the king and what belongs to the state. But, note that the king must spend a lot on social services (free healthcare, free education (both local and foreign) in Saudi Arabia, etc., to please his countrymen, lest they revolt.
The House of Saud is sitting on the real money printer.