Walmart. Walmart is totally the winner in this category. It has all of the grocery store things you mentioned plus mountains of clothing, household goods, mind blowing technology, medicines...
Show them all of these wonders - then tell them that this is where poor people shop.
Last year I read some fan fiction in which a young woman comes isekai-style from a medievalish fantasy world to present-day Nevada. To make a long story short, one thing she concludes during this experience is that God wishes to bless everyone with ... a CostCo!
Yes, it's called "in His strength, I will dare and dare and dare until I die"¹ in the Glowfic Constellation. There are a whole bunch of people there writing about characters and settings from the RPG Pathfinder (which I haven't played), most often in an isekai scenario (people from our world enter the RPG world, or vice versa).
Although I was fascinated by some elements of this story, it was actually abandoned incomplete last September and it's unlikely to ever be finished, so you may be disappointed by that if you get into it.
(Some people who play Pathfinder also complained that they didn't feel the characters were faithful to the originals, which I can't really evaluate.)
¹ A quote from Shaw's version of Joan of Arc, which is pretty thematic, although the "He" in question for the title character of this story is a particular god from a polytheistic pantheon.
Show them all of these wonders - then tell them that this is where poor people shop.