Sounds to me like someone at Amazon is good at marketing. Let a few things go for an insane deal, knowing it will hit the front page of every blog. Then reap the rush of next years prime day with people scouring the site for pricing "errors". Pretty cheap and effective marketing. Kind of like a raffle but without having to get all the lawyers involved to make sure you comply with raffle laws.
Ah yes, finally someone will be talking about Amazon and Prime Day.