The one-2-many issue: The reason given by this Dutch guy to speak up and start his YT channel - the guy having hundreds of children - was the increased chance his children meet each other and start a relationship and make babies. He was discovered without nobody knowing he had that many children. A big drama in the news back then. The documentary I still have to watch.

Black market isn't the best I can imagine, but a more 'efficient' way instead of waiting gazillion years for a donor? When you find the documentary, please drop the info, I am interested!