Human mercs cost the same because they can run and use more variety of weapons.
Quite the opposite, human mercenaries can't really utilize m60 when it comes to BG, mutants can do that and as well wield lsw, flamer is just non practical for either. Human BG mercs could really use better armor, i wouldn't actually mind to see them running around in CA just to have some kind of advantage over mutants, simply running is not enough. We both know how they are used => spawned in weapon range where speed is not of importance