I think that this means that everything in B B and Beyond is overpriced by 20 percent since you can keep going back and buying it at a "20 percent discount" if you are willing to put in the effort. Comparison shopping can show whether things in this store are overpriced compared to the market.
Every BBB I've been in lets you use at least 5 coupons when you buy things. You can also use expired coupons.Mary is partly right in my experience; there are some items (notably small appliances) where BBB seems to mark things up by 20% compared to other stores. On the other hand their prices are pretty competitive in other areas (dish cloths, knives) so I find the coupons worth it.
The coupons clearly say one per customer per visit in fine print. I don't really have the nerve to try and violate the stated conditions although I have heard that the expiration dates aren't enforeced.
They really don't care if you use more coupons, actually, since most likely some of the things you are buying are at a big markup. They are banking on the fact that people get into the store then buy other things they hadn't thought about. Most people do not go into a store for just one thing.