I find that construction odd. Are you trying to say all goals of war are ultimately economic? If so I think that's needlessly restrictive.
>Because whatever value those peoples derived from conflict wasn't most likely in increased treasuries, but instead in the extension of land and in the number of subjects...
I know next to nothing about Assyria, but the Roman treasury profited quite handsomely from conquest, to the point that in the Republic's most expansive period you only had to work two days a year as a Roman citizen to pay your taxes.
Because when the Romans conquered a people they took everything that wasn't nailed down, sold the land, sold the rights to collect taxes in that area, and then sold people themselves.