Hey there,
Check out this Website I posted below, it has a 'Cost of Raising a Child Calculator'.
http://www.babycenter.com/cost-of-raising-child-calculator
Good Luck.
ANSWER
Alot also depends on whether you borrow a lot of things off family and friends, or buy second hand, and whether or not you breastfeed and use cloth diapers.
I have always used preloved furniture and clothes (but always bought a new mattress) for my children and breastfed for the first year (at least) and each subsequent baby has used the clothess from the last baby - so my children dont really start costing me until they get to school, then my wallet is out alot lol!
AN example -- a bottle fed / disposable diapered baby will cost (depending on where you live) upwards of $40 a week just for food and diapers - where as a breastfed cloth diapered baby is free (not counting the inital outlay of the cloth diapers and an extra load of washing every 2nd day)