the bottles are the same for every age, the only thing that changes on them is the size of the nipple, for that young its the slow, then you go to medium around 5-6 months and fast when they get older. it just means, that the hole starts really small and gets bigger (meaning the little ones have to suck harder to get the formula). anyways, bottles normally cost anywhere from $1 a bottle (dollar store/walmart) - $50 for a pack of the more expensive brands. it really depends on what you are looking, theres just way too big a diff in cost to give a definate answer. sorry if that doesn't help at all, but thats the best i got.
at 12:32 AM on May. 3, 2009