Cyborg -- you just raised an excellent point. Yes, adoption is cheaper than going the infertility treatment route. HOWEVER!!! lol. All sentimentality aside, ISN'T DNA like, um, the key argument for bad behavior, obesity, gayness, ad nauseum? In adoption, therefore, when one adopts, the baby has "two questionable" gene pools. Via "fertility" treatment, the variables is reduced. Nonetheless, people don't seem realize that while nature plays a role, it can reach back several generations to draw upon.
That's a good point about not knowing the history of the people that gave up the baby,etc. I don't doubt that's a factor in why some people do the treatments.