That part is pretty hard to understand. Moral considerations aside, the sheer expense of abortion vs. contraception would seem to be a deterrent.
For the middle and upper-middle class it doesn't matter - most major medical insurers will pay for it.
I was quite disgusted, but not at all surprised, to learn that my own insurance would pay 100% for an elective abortion - yet a common hormonal contraceptive costs me $20/month copay plus about $250/year in premiums towards prescription drug coverage (to be fair, the premiums cover both me and my husband).
Of course this doesn't work for high schoolers or college students still on their parents' insurance, because then Mom and Dad would see the insurance statements. Abortion is covered by insurers for those women who should know better - women who are educated, who work, and who ought to know that if they're having sex at a time in life where children are not wanted, they need to use contraception.
Don't forget, there's no expense if the gubmint (aka us) is paying for it. And there's not just Medicaid or 'Welfare'. All those 'free clinics' get gubmint funding (grants, etc) too.