The article is not about folk tales of "living within your means". It is about paying more for the same thing because of various factors like whether you can afford to transport yourself to a better store, whether you have the space to transport and store bulk goods, or the working funds to afford bulk purchases, and whether your dwelling even has a kitchen or refrigerator.
A large chain grocery store will usually have better prices than a corner grocer / convenient / liquor store. Some people have to do some grocery shopping there because they can't commute to a Jewel, Safeway, etc.
