There are plenty of other differences between the shopping experience at Wal-Mart and Costco. A peculiarity of local geography is that we find that the two Costco stores at our end of the Twin Cities metropolitan area are just never on our way to anywhere else, so we let our Costco membership lapse after just one year. For quite the same reason, we hardly ever shop at Wal-Mart. But we shop at Sam's Club (the Wal-Mart version of a warehouse store like Costco) all the time, simply because it is on my way to work and largely on the way to many of our other trips during the week. Today we built a trip to Aldi into our schedule while our daughter was at soccer practice about halfway from our house to that store. We love to minimize driving--driving costs both money and time. Some stores cannot thrive unless they are within SHORT drives of many customers. Some of those stores have to extract a lot of productivity out of each worker to pay the workers even minimum wage.
I still wonder when Amazon is going to go all-in in setting up major same-day delivery centers in most metropolitan areas in the United States. That could have a revolutionary influence on my shopping habits. And if robots can do more of the stocking of shelves, and eventually self-driving cars do most of the delivering, that business model could end up with huge market share. I'm very happy when workers at menial retail jobs are paid more--I have had such jobs (at Sears and at Target, many years ago). But they best gain opportunity to advance themselves economically when they also can save on their own consumer spending in retail stores. Everyone likes low prices day in and day out.