I don't have a link for this. Sorry if that breaks the rules, but I got the idea for this from another post here. SM commented on the price of groceries...
There was a bit on HLN quite some time ago on "couponing". It also got into how stores are out to move some different products and that coupons sometimes link products together. "If you buy this for $20 bucks, you also get 1 of these for 1/2 off".
The concept was like a budget. Get only products you need and or use on a regular basis. If you've never used paper towels or paper napkins, who cares what they cost and what goes with them.... Stick with the necessities, and only spend money on things you use..
They then went into a national grocery store chain with a fabricated list that resembled what a regular family of 4
might need to get through a 2 week span (traditional pay span). She found a "buy one get one free" bag of chicken legs. Normally it was like $6 per bag, so she got 2 bags for $6, plus she had a manufacturers coupon for 1 dollar off for this particular item. In fact, each thing they got in the store had a similar situation. If it wasn't on sale, she had a coupon. If she didn't have a coupon, she bought the lowest priced item on the shelf, bypassing brand names.
She sent another person out with the same list of things to get, but told them to "shop" without concern to price. They compared the prices at the end of the bit and the coupon lady saved something like $85 bucks over the "regular shopper". They also compared "necessities".
The moral of the story is, if you coupon, you need to be vigilant... buy only what you need and bring all of the coupons you can. "Desperate times take desperate measures"... might have been the title of the bit. That's what they closed with.