Sales are different, and yes, a good sale or promotion or coupon - and all bets are off as far as expense.
But they WANT to hook you on the product at the sale price or promotional price, it is not that the actual item is cheaper, just that they are willing to sell it to you at a loss at first until you see the ease and convenience and taste of buying their highly processed crap - and when you buy it NOT on sale or promotion - they make their money back and more.
I only buy it when it's on sale. See, I'm smarter than the stores.