Why would anyone use baby's formula over evaporated milk?
100 ml enfamil = 500 calories, while 400 ml of evaporated milk = 500 calories + more protein + vitamins/minerals
Baby formula isn't just about the number of calories. More protein isn't necessarily better - only about 10%-15% of a baby's calories should come from protein and that's about what breast milk provides (the composition of breast milk actually changes over time to meet the needs of the nursing infant - this is one reason why there can never be a perfect baby formula) - the majority should come from fat.
And baby formulas are heavily fortified with vitamins and minerals in the amounts which are appropriate for infants (which isn't the same as the amount which is appropriate for adults). There are strict standards set down for the manufacture of baby formula to ensure that it provides the right amounts of fat, protein, carbs, vitamins and minerals for infants.
Also, what ratio of evaporated milk to water are you using to make your calculations and what ratio of Enfamil powder to water?