I don’t think anyone is saying the baby would be better off dead, just that this is not an acceptable alternative to abortion and it isn’t morally better to traffic humans than it is to kill them; either way, the human being in question becomes an object to be abused. On one level, the outcome is different and you’re right in that this way the child has more hope and a chance at life, but that doesn’t mean it’s morally better, especially when there are options that bypass any human rights violations.
Adoption is a good alternative. And if those people are that eager to buy a baby, they would have been just as eager to a listing that said, “Adopt our child, we will transfer custody to you, all we ask is that you help us with the medical bills and legal fees.”