Having just recently worked at a grocery store, they’re likely shooting for being able to change prices daily without having to pay 3 extra workers to change all the tags in the grocery store. So it likely wont change during the day, for the reasons you listed, but any chance they get to up the price without a percieved loss in customers, they’ll just hit a button and bam, jacked the price by a dollar
Did OP update their post? Because this post is 99% what OP said in theirs