Not that I agree with the idea of paying off people, but Syria's total GDP is only about US$60 billion, hard to imagine that it would take "trillions".
I was going off of a quick Google search of Bashar al-Assad's personal wealth, which led to an MSN article putting it at $112 billion (http://money.ca.msn.com/savings-debt/gallery/dictators-and-t...). Since huge chunks of the economy are controlled by the Assad family and close associates, and have been for decades, I figured that it would be reasonable to assume they had accumulated hundreds of billions of dollars by now.