Here in Germany, we don't have walmart. There are discount markets, but those save money by buying in huge bulks, and by only selling a small sortiment of stuff, especially the food discounters. The two biggest discounters, Aldi and Lidl, both have only 2-3 choices for each item, and until recently, you couldn't even get coca cola and other brand products in Aldi, only their own no name stuff.
You can also get food for low prices at smaller shops, and while you might miss out on some small savings, you get more choices and the quality is often better.
As is said in the video I posted, low prices aren't free. If you don't pay for the profits, the people who manufacture the goods do, or the people who sell them to you, or the products are produced in a cheap manner. (which doesn't have to mean that they are of a low quality, but those animals from which your meat came most likely didn't live a happy life on the farm, to put it this way...)
There are many reasons to pay more than you have to.
To use an analogue: I am a roleplayer, a reader of fantasy novels and a sometimes player of tabletop wargames (warhammer and warmachine). There is a shop in my small city who sells supplies for each of those hobbies, books for roleplaying and reading, dice, music, figurines for tabletop and so on. It also has space set apart for people to engage in wargaming, roleplaying and trading card gaming.
Now, are they cheaper than any alternative? No, they are not. I could buy my books and other supplies online, and most likely shave off 10% from any purchase. But I still make a point of buying there, or ordering stuff trough them, because with those few extra euros, I pay for the continued existense of this place, which also provides me with a very convenient place for talking about my hobbies and play them.