The al Sauds are not a monolith. While there are princelings who hope to ascend the throne by using third parties, including perhaps Islamist terrorists, I doubt the guy in charge really wants to rock the boat. There are probably plenty of wealthy non-royal Saudis harboring ambitions of their own, including perhaps parts of the bin Laden family. After all, in an oil-producing country where the government owns the oil, power is money.
As to what pros can do with limited resources, I'd point to the Bali bombing. 200 dead in a nightclub vs 3 dead at a road race. I think it's pretty clear that the nightclub bombing is far more frightening.
How in the world can that be clear at all ? You are comparing the terror experienced in one country and culture to another country ? Let me know when you shift is over.