There are a million kind of birth control pills. Cost depends on which one your doctors picks for you.
Ok, so what about a rough guess?
On the men's side of things, WalGreens website says a box of 36 Trojans will go for about $21. At that price, you could do it once a day and come in at under $20/mo. Seems silly for the gov't to subsidize it.
Kids cost the gov't a heckuva lot more. Better to nip that one in the bud. And people in relationships frequently refuse to use condoms. Defeats the entire purpose of being monogamous.