> BTW, the article is paywalled. I have no idea how a grocery store is going to adjust prices at checkout, as the prices are marked.

Many stores are rolling out electronic price tags on the shelves, which can be rapidly updated wirelessly [1]. They could probably do the price adjustment there. I'd assume they wouldn't want to make it too blatant, which would be a challenge.

[1] https://www.businessinsider.com/walmart-digital-price-tag-sh...