Amazon in America is offering $5 off a purchase if the user orders via their mobile app. As of Saturday, if you go to Macy’s or Toys R Us and physically scan an item’s barcode with the Amazon App, Amazon will give you up to $5 off that item if you add it to your (mobile) cart and leave Macy’s empty handed.

This is about as aggressive as business gets: if you walk into a competing retailer, scan the very item they’ve spent money on to put in store, we’ll do you a better deal today. Does pricing get any more predatory? Amazon don’t want to be a major retail player online, they want to be the retail player, period. eBay and Google can play around with physical pop up shops, but not Amazon. They know where their expertise lie: online. And they aren’t shy about getting you there either.

It’s yet another stunning lesson from Bezos of using market-leader advantage to further leverage your position. The banks are claiming “Caveat emptor,” or buyers beware, as a retort to the mis-selling and exploitation critique. I can’t help but think Amazon will be saying, ‘sellers beware,’ in the coming years as they turn retailers’ own guns back on them having mined the data to within an inch of its life.