The Vikings make a deal with charles the fat and it's the exact same sort of deal they asked for before this entire 11 month siege even started. The economic costs are unquantifiable if we want to get a little teeny window into what the cost might look like historian dan jones in his book powers and thrones quotes another historian who estimates that 14% of all the silver pennies minted by the entire frankish empire over the entire century of the eight hundreds went to pay off the vikings just for protection money just for go away funds.