So, you should totally read the update I made to my last post. Science has pretty much proven the system of two bullis per pillage per soldier would actually do more damage to your own infrastructure than your enemy, vastly more as it were, though as stated in the post that's without factoring in crop displacement because the specifics of how raiding damages production is not stated anywhere I can find it. The Crusaders were certainly raiders and, for a time, made an incredible amount of money killing innocents and stealing their stuff. :P

EDIT: 

Even without armor, a guy with a bow and a dagger still costs more than two bullis per season to field. Twice as much, to be exact.