The difference I see with more upper class stores especially ones like Whole Foods is they tend to be in dense layouts where it is literally more time efficient to get your shopping done, and the stores are frequently placed on higher value property which is closer to the wealthy patrons. They tend to have a good selection of healthful foods maybe with pricy grass fed animal products with a higher ratio of omega3s, nitrate free cured meats, food for special diets like gluten-free, and all variety of things which are in a certain sense practical. Also generally the food of equal nutritional value tends to taste better, which makes it easier to stomach your conscientious diet.
If your wealth is such that food cost is a fairly negligible part of your expenses, USUALLY the Walmart will be further away located on less expensive real estate, roaming around the Walmart supercenter can literally take more time (both of these points are, to be fair eliminated by curbside pickup/delivery), the variety might be good but it's of foods that might not necessarily be worth the cost savings, the meat & produce might be alright but it's rarely going to be exceptional. It's not that any cook worth their salt can't go to Walmart and cook some fantastic food, it's that the real fancy store can be the path of least resistance.
I patronize both stores, tending to make runs to Walmart type stores for mostly non-perishables sold at superior prices. Honestly I feel more uncomfortable among wealthy patrons can poor ones. I can feel a miasma of snootiness around me in an upscale enough shop.