The money the vikings directly stull are looted in their many many many attacks doesn't include any of the money that the empire had to spend to defend themselves or fight them. 14% of all the silver pennies in direct payments for protection is spent on protecting itself and its people from the Vikings. The nine hundred looks particularly scary if you are a viking opponent according to some historians. If you're a viking you may be hearing ominous darth vader music going into the nine hundreds as well we quoted a couple of recent historians who point out that theVikings were well aware that their culture and belief system was under siege.