Seems to me that casulties done by arrow fire heals alot more than casulties done by a falx. Say I loose 40 archers from arrows, maybe 30 - 35 heals. Take the same casulties done by falxmen, maybe 2 or 3 heal.
An arrow can be pulled out and a doctor can heal the wound, a falx can cut off a limb/cleave a man in two, kinda hard to heal him and make him fight again.
So it seems like there's some sense in the calculations, but I don't know how it is calculated exactly.
Sparta
"One can do without God, but not without religion.."
"Never interrupt your enemy when he is making a mistake."
"In war there is but one favorable moment; the great art is to seize it!"
- Napoleon Bonaparte