Confused about formula

I was comparing two kinds of formula, the enfamil powdered 900 g and the parents choice powdered 900 g. The enfamil costs almost $30.00 while the parents choice costs $15.00 so basically parents choice is half price. I decided to compare vitamins between the two and they are literally the exact same aside from enfamil lists vitamin b12 and parents choice does not. But I read that vitamin b12 is naturally occurring in cows milk, so because they both use lactose and enfamil uses modified milk ingredients and parents choice uses skim milk would that mean it is still in both because it’s part of cows milk in general and enfamil just adds extra or is there none at all in the parents choice?