Also, it's not as if the chroniclers of that period would have an easy time getting accurate records. They would have access to commentaries written by the general (Caesar was not the first to do this), but obviously these weren't impartial. Sometimes the best the historian could hope for was to find out how many slaves were sold afterwards. Of course, that number would have included stable boys, armourers, ox-cart drivers, etc. Eastern armies did tend to have a lot of those, so part of the inflation could have come from there.