If the state owned oil companies pay a lot to the royal family, that's kind of like you owning the company and setting your own salary to whatever you want. There's a difference on paper, but not in spirit (to me anyway).
Just as an example, Prince Waleeds fortune is more or less self made. Furthermore, his company "Kingdom Holding" (IIRC) is to my knowledge not owned by the government (but it's a public company so that big investment fund - is it called the PIF? - could theoretically buy KH stock.)
Some of those real estate projects look private to me.