Yeah. Put it like this: if you are paid $50/hr (which is a very low end for this audience on HN), and you see some $2 coupon not applied, you'd need to be able to resolve it in less than 3 minutes for it to make sense to dispute (in a purely holistic sense. ofc time is invaluable for many).

If this is on some normal $200 grocery receipt you probably won't be able to find the mistake in 3 minutes, let alone go back and take the time to flag a busy cashier, find a manager, and resolve the error. At best, it'd be a lesson learned to check at scan time extra hard.