Hi J.,
It really depends on what type of day care you go to. Some are better than others and its always more expensive the first year of care while they are infants. My daughter goes to Bright Horizons in King of Prussia and for 3 full days (she is 2) I pay $950 a month. Its expensive but this daycare is top notch! It also includes snacks, drinks and a hot lunch. When she was an infant, I would say add another $75-$100 to this a month.
Other centers I priced such as Goddard School, Malvern School, Chesterbrook are slightly less, maybe $100 less a month when she was an infant. There are other places such as the YMCA which I know are cheaper. But, you get what you pay for. I would DEFINITELY start making calls once you know you are pregnant, if not sooner cause a lot of places are full and are on 1-3 yr wait lists! Good luck!
K.