This particular grocery chain sells gigantic frozen shrimp in two pound bags for $19.95.

Because of the lay-out of these stores, it would be possible for a miscreant to purchase a few cheap items, and then wheel his/her cart back around to get some single "forgotten" item, and while doing so, stuff two or three bags of shrimp into the bags holding the purchased items, and then check out again with something like a bottle of wine or a six-pack to go along with the shrimp. And if the person was using spacious reusable fabric shopping bags, which this chain sells for .99, it woud be even easier.