My concern isn't that the price of an item will go up between my grabbing it and checking out, my concern is that they'll update the price before I ever see it, and I'll pay 50 cents more for this box of graham crackers than everyone else. After all, Walmart knows that I buy graham crackers every time I go there, and they know that I've put up with price increases in the past. They know who and where I am from the moment I enter the store to the moment I leave.

There is nothing stopping them from bumping up the price of those graham crackers while nobody is in the aisle. I grab them while they say $8.59, and I pay $8.59 at the register. Someone else who tends to buy them when they're on sale grabs them while they say $7.59, and we pay different amounts at the same time, because Walmart also knows what register I'm using and which list of prices to charge me.