The HV told me at DD's 1 yo checkup, that I should be putting her on cows milk as well as giving multivitamins, as cows milk doesn't have the same level of nutrients as formula. I was giving her formula at this stage, but was told that I should try and get her on cows milk. Go figure.
So, I kept DD on formula - which is easier for me to prepare as I am not comfortable with heating every bottle of cows milk in the microwave. I think the cost is comparative. DD has 1 or 2 bottles a day (7oz each) and we use one container a week (£7).