Protectorates count to your provinces, as Emperor Umoi has pointed out, and they get you money. I think you get the money the protectorate faction makes. So, if you´re unlucky, they might cost you money if their faction has a negative balance. Personally, I´ve always profited from being Protector, but not close to 50 million, 50000 from four protectorates, among them Egypt, is more like it. Their income is stated as diplomatic/tribute.