It is legal in the United States to pay for gametes - sperm and eggs - with the purpose of allowing infertile people to procreate. Adoption is also legal. But it's illegal to sell a baby. This makes no sense. I don't mean selling a child in terms of "ownership" of the child, I mean selling a baby to allow the baby to be raised as a child by the buyers. Why is this logical? Gametes have no purpose other than making babies, so materials solely for making babies can be sold, but babies can't? Is there any other example of this anywhere in the US? Certainly some drugs can't be sold, but materials for making drugs have other potential legitimate uses, and those that don't are generally illegal. Even the stuff sold in drug paraphernalia shops can be used for smoking tobacco.
Refuting obvious argument number 1: you could quite easily ensure that the baby has to be sold before birth or within a short time after birth, so that the baby doesn't connect to the biological parents and is raised entirely by the new parents. This avoids the cruelty of selling a 10 year old with connections to his/her family.