IMO: The point is that they KNOW 96 out 100 were able to make a purchase and have the products ship to them. The 4 that weren't able to make a purchase is irrelevant to the 96 who did.
IMO: wouldn't take long before they'll be buying it for each other or selling to each other. Thus it establishes a black market and organized network of sellers and buyers within the youth groups. Where the same products are still available.
Come to think of it, if a teen used an adult's credit card to buy stuff the packages would arrive addressed with the name of the adult. You would need the adult's OK for that to work. In which case the adult could order them and give them to the kid.
Maybe their point is just that if parents are willing to break the law to buy forbidden stuff for their kids the only way to stop them is to stop the product being sold. All makes sense in a horrible nightmare sort of way.