alt Hacker NewsI suspect there is actually three groups, because the app also has a sort of coupon-ing in it. The lowest price requires you to search the app to find a "deal" that is currently available, rather than just use your loyalty points to get a discount.
One of the ideas of classic coupons was to offer a lower price to the most price sensitive customers. The people willing to deal with the fuss of finding and cutting out the coupons.
Also, EBT payments allegedly cannot use coupons. I suspect they figure EBT customers are willing to pay more, so they raised menu prices a lot but also offered steep discounts to everyone else.