I would bet that the money maker isn't the actual technology. The data they could collect on consumer shopping habits, tied automatically to a cross-store profile + an expanded Amazon SSP/DSP would create huge value to Amazon and brands. Added onto their already fast growing advertising business.

If this is in fact their revenue play they could even sell this at a loss just to build up the ecosystem, get a unmovable majority monopoly on the tech -> and data.

Maybe even add on top something like Good RX where retailers pay amazon on top to drive traffic to their stores. And even combine with Brands who want to offer discounts. Double dip.