A shelf label showing one price for loyalty members and a higher one for everybody else is now standard in American grocery. The split exists because the two prices are paying for different things, and only one of them is a straightforward retail transaction.
The discount buys identified purchase data
Without a card, a basket is anonymous. The retailer knows what was sold but not who bought it, what else that household buys or how often it returns.
Scanning a card attaches the basket to a household, and a long history of baskets is far more valuable than any single transaction.
The lower price is what the retailer pays for that identification, which is why the same goods can be sold at two prices in the same aisle without either being a mistake.
Suppliers fund a large share of it
Many loyalty prices are not funded by the retailer at all. Brands pay for temporary reductions to move volume, defend shelf space or respond to a competitor.
Routing that money through the loyalty programme lets the brand see who responded, which is information a general price cut cannot provide.
It also lets the reduction be withdrawn cleanly at the end of the period without the retailer having to explain a price rise on the shelf.
Personalised offers segment the customer base
Once households are identified, offers can be targeted. A shopper who never buys a category can be given a deep discount to try it, while a loyal buyer of the same product receives nothing.
This is more efficient than a blanket reduction, which pays a discount to people who would have bought at full price anyway.
The consequence is that two cardholders in the same store can be offered materially different prices, based on what each has bought before.
The non-member price becomes an anchor
The higher price is not really an expectation of what non-members will pay. Comparatively few baskets go through without a card.
Its function is to make the member price read as a saving each time it appears, which reinforces the habit of scanning the card.
Because it is rarely paid, the non-member price can drift upward with less resistance than a single posted price would meet.
Where the exchange sits for the shopper
The arrangement is a trade rather than a giveaway. A household exchanges a detailed record of its purchases for prices that would otherwise be the shelf price.
Whether that is worth doing depends on how much of the basket is actually discounted, which varies enormously between stores and between weeks.
What is consistent is that the data outlives the discount. The offer ends, and the purchase history remains.