Do they offer a contract to make up for the loss of access to other customers?
Because that's a factor. If nobody else can buy your goods, they eventually consider your goods to be inaccessible at all, and you have no other customers.
Me? I'm going to be honest in a retail environment and tell the person they can't have everything because it essentially shuts down my business entirely until I can restock, which means I have to rely on that sale covering the expenses in between as well as lost custom as a fallout of essentially being closed until new goods arrive.
It isn't just unfair to other consumers, it's problematic on a smaller scale.
That's different than the scale apple works on though. The suppliers don't have to worry about that, so they can get away with saying fuck the other customers because the other customers are on a similar scale.