There are certain baseline units which the other variants are based off (KoM shieldwall regiment, ogre warriors, zombies) and the RC then tweak points to take into account synergies within armies etc (its why comparable units in different armies arent always the same points).
Similarly the scaling in points/stats from regiments to the other unit sizes are pretty consistent.
There is however no published formula or baseline equation, coupled with the fact that points etc have been changed in the CoK updates etc.
In most wargames which have “build your own unit” type generation, the ones you could create are more expensive than identical ‘original’ variants.