Yes, the fed issues currency by fiat, but the actual resources consumed by this war probably account for the monetary price tag. Additionally, the money spent did not vanish in a puff of smoke at the end of a gun: it lined the war chests of the military industrial complex. This gives these people and organizations outsized influence to manipulate our government into staying in wars in order to justify buying expensive munitions. This destructive feedback loop is the true cost of war.