While a lot of stores have the "one coupon per purchase" rule there are several chains that have "Double Coupon Days" sales where you can use multiple coupons.
There are also times where customers can use Store Coupons and Manufacturer Coupons together, thus allowing for multiple discounts. Some of those coupons say things like "Maximum 5 items per coupon" which is why you have to buy 50 mustards. Each coupon gets you x amount off and after some point that tips it into the world of crazy discounts that I can't wrap my head around.

Also: There are Membership Cards like at Safeway, CVS and basically every other store now which give you discounts on top of the coupons that you bring in, or that give you coupons for spending certain amounts.

The Extreme Couponers use all these things together to get the best possible discount.
Slightly off topic rant:
I worked retail for years (though not in a grocery store) and semi-regularly dealt with people who insisted on getting a discount despite the fact that the coupon wasn't active yet. I know there were times when a customer wanted to buy a bed set with a coupon that wasn't active yet and we had to explain that we couldn't honor it. We'd then explain that the item was on Sale TODAY for 10% off but TOMORROW it was full price, which is when they could use their 10% off coupon. Still people would insist that we honor the coupon, so we would, but off of the original price, which they didn't like. They'd want the 10% off with another 10% off. This was generally a difference in price of about .50 and they'd get to a point of almost yelling(or just straight up yelling) because we weren't "honoring the coupon".

It seems to vary from CVS to CVS for me. I've had some clerks tell me they won't pair the off (or off ) with some other CVS coupon, while others have flat out said they will take double coupons for something even if that coupon doesn't "apply" to the product. I've had one tell me they don't care if some coupon expires by a certain date, they'd take it up to a week afterward.

Also these types of "extreme couponing" incidents are not an everyday occurrence. You might get a decent deal if you're looking and actually need the product. But it's no better than those people who print out internet coupons and pair them with whatever comes out of the paper or the grocery store ad. For the most part, you have to buy to "save."

Buy one, get the second 50% OFF! YOU'LL SAVE MONEY!

My then-mom-in-law was like this.. I really don't think it's fair if you don't have to clip the coupons yourself like she did. It's kind of like complaining about having to pay an electronic service like HRblock for their services when people who actually manually do their taxes have to pay nothing (except their taxes..)

Anyway she'd religiously cut these coupons and tell us about all the deals when we'd visit them, me being bored as fuck (wooow!) but one day I went in with her because I needed cigarettes and I get to the front and she's in a screaming match with the poor Walgreens clerk because of some coupon loophole.. it ended with her saying "Last week I had a problem with my coupons. This week I have a problem with YOU."

Embearassed, I walk up "Winston Lights..."

I work at CVS/Pharmacy until Friday, when I will finally leave. Extreme couponers disgust me, at least the ones like this that are happy and proud and make it hobby. Anyone just saving money on shit they need is obviously fine by me.

Anyway, let me break this shit down for you magnesium. Manufacturer's coupons (the one some rep stuck on the bottle in this video, or the one's you get from the paper) are all basically limit one per item, fine print, etc. CVS is going to mail those in to the manufacturers in exchange for real money, so we have to follow their rules especially regarding expiration dates or else they'll audit us and stop paying.

The white paper coupons she has are store coupons that CVS itself issues to get people to buy useless shit. CVS just eats the cost of those anyway, they're there to drive sales and give happy thoughts to consumers like this one, so we don't really bother sticking to the fine print. The cashier is a manager of some sort, all that beeping is her using her override to take the store coupons. She sees she's being filmed and wants to play along. Plus, although she's only getting ##CONTENT##.93 cash outta the lady, she's going to turn in that coupon, so the store might still be making money on this purchase.

Il fiore bel: You can pair the off with the off (without an override) as long as you spend . That's also true of the category specific $x off $x coupons, so if you have a off deodorant coupon, you would have to spend before you could pair it with a off coupon. Since we're eating the cost of those coupons anyway, we generally don't give a shit about expiration dates on store coupons, with some exceptions where pairing it with a big sale would make us lose money. As long as they get you to buy, they're working and we want to take them. That said, culture varies a lot between stores and your cashier may be a stickler because someone told them to be, or because no one told them not to be. Also just because of general bitterness, or because you're being an ass, or because they're an ass.

Lastly, these types of "extreme couponing" incidents absolutely are an everyday occurrence, usually a several time per hour occurrence. This one is not exceptional. Exceptional is when someone brought in a photo copy of some IL statutes to get free charcoal without buying a lot of Budweiser to earn it. Exceptional is the 20-year old kid who spent about 10 hours a week physically in my store and god knows how long at others, and god knows how long online, just couponing (fucker was on disability, but could still work a full-time job's hours being a worthless shit). Having talked at some length to both, I honestly prefer professional shoplifters. And I definitely think they are less harmful to society.

I quit my convenience store gig due to the desperate lifestyle of my customers, who simply could not be helped, but cigarette couponers are absolutely the worst. The cigarette companies send them these absolutely useless coupons that nobody but Wal-Mart or Safeway takes, but the couponers won't buy their cigs there, because of mark-up.

Absolutely no conversation that ever started with "WHAT'S YOUR CHEAPEST CIGS?" ever went well, and the worst question of all was "WHAT'S YOUR CHEAPEST ROLLING TOBACCO I DON'T NEED PAPERS".

Hey, I'm very nice when I ask for the cheapest pack of cigarettes.

Granted, graveyards at a 711 was my first job at the tender age of 17, so I have more than a little empathy for cashiers and do my best to get what I need and get the fuck out of their way.

The cashier experience is why someone has to put a gun to my head to force me to cut and use a coupon, and why I apologize profusely for being garbage life to the cashier if I ever have to use one.

Remember those fucking coupon dispenser machines that left coupons all over the place in stores like Apollo 13 just got back?

LJ: I had a lady come in every morning at around 5:30 AM, after I'd mopped the floors and just before the morning coffee rush. She must have been a hardcore alcoholic because she would get a small cappuccino and proceed to spill it all over herself and my nice clean floor. I watched her do it for about three days, then I started putting a small amount of coffee in an extra large cup, bringing it back to cash and ringing her through at the small price.

I won't lie and say that I was more concerned with her burning herself than with cleaning up after her, but it was pretty close to 50/50.

Oh, she spilled the coffee because she was shaking like a Parkinsons' victim every damn day.

The only customers that really bothered me were the smart-asses who would come in at 2 AM and ask "Do you ever worry about getting robbed?" I mean shit, I tried not to think about it, and 2 AM isn't the time to start.