But that explanation is actually misleading. I've had items that I ordered previously from Amazon suddenly turn into add-ons at the same or even slightly higher

But that explanation is actually misleading. I've had items that I ordered previously from Amazon suddenly turn into add-ons at the same or even slightly higher prices. Amazon may well have decided to create the add-on program in lieu of removing them, but "wouldn't even exist" isn't the entire truth, as it doesn't acknowledge the fact that the items did exist before.