The amount of "discount" is so much that they must be getting a large income stream from the data. Whenever I see something where the shelf sticker claims a lower price for "digital coupon" (meaning: use their app), I put the item back onto the shelf and move on. I'm willing to use the loyalty cards, but I am not willing to allow the sort of surveillance data that phone apps provide.

Margins on items at grocery stores is pretty thin. For them to be able to offer 50¢ or $1 off for items by using their app, that tells me that they are making more than that much from the data about me. My suspicion is that they're earning at least 10x that much from the data.