Assuming there's no legitimate IP infringement going on, then it's not different as far as I can tell. In my view, if the Amazon store is so big that it can use

Assuming there's no legitimate IP infringement going on, then it's not different as far as I can tell. In my view, if the Amazon store is so big that it can use its market power to make the market worse (for buyers, sellers, or both), then make that argument on its own. The specific practice of noticing that popular third-party items can be offered by the store at a lower price isn't a problem in my view. If the convenience store on the corner sells homemade cookies cheaper than the Oreos on the shelf, is that really a problem?