I have been struggling to keep my weight from going up and changing supermarkets has had an unexpected benefit. I can't get a daily special on cookies and snacks so I don't eat them. Suddenly my weight is stabilizing and I think maybe going down. Those Daily Special cookies were making me fat! Not only that but I spend much less on food now. I have to keep fresh baking available but I can whip up a batch of cookies in flash at this point, so it's not a big chore.
That's when a good deal isn't so good in the long run. If it keeps you over buying and over eating, it's bad for you.