calculate the amount of money you need for the gynae package and the delivery, pick the one for emergency c-section, just in case.
add up all the costs for the baby things: cots, clothes, etc, jabs, diapers, formula milk (if you're not bfing).
And round up the amount.
Tell him that that's only the expenses of having a baby, and doesn't include the monthly maintenance that he should be giving his child.
And most importantly, ask that guy to keep his d**k locked inside his pants if he doesn't want to have kids!!!