fwiw my understanding was “if people are willing to go black/grey market for it it must be lucrative and/or a thing people greatly need!” and my answer to THAT question is:

it is very lucrative for the clinic. You’ll get some pocket change, similar to the cut a hooker gets from her pimp. Now, they are doing an important service to you and the client in terms of keeping you out of child support but also out of the child’s life without the consent of the parents (until 16-18, as you said). They’re also attending to some sexual health and genetic concerns. But they’re almost definitely not providing enough benefit to justify their cut. Fertility medicine is very lucrative as I understand.