score:56
The claim comes from Machiavelli, and, for example, this site criticizes it. In this case, Machiavelli was arguing in favor of training militias instead of using mercenary forces. A similar case is Battle of Anghiari, where it is claimed that only one man died. This Wikipedia article offers some explanations:
As for why was there more attention to knights / men-at-arms / condottieri casualties then to infantry, there may be several factors: