I do shop at Costco, but not a fanatic.
However, I love COST. My single 5 figure purchase in fall of 2017 is up 6.5X, roughly 30% per year. If that continues for 15 more years when I retire, I'll be sitting on $3m.+
In the store, we get their TP/paper towels/napkins, chimichangas, their chicken bake sandwiches, bags of popcorn, granola bars, nuts, chips, wine/beer.
Also usually once a year we'll get clothes. They have great prices on kids winter stuff.
We don't venture into the fresh stuff as much. And never the meat.. it seems pricey to me, but I am one who only buys meat on sale at a regular store. I get ground beef for $3 or less, ribeyes or sirloins for $5-$7/lb, shrimp for $6, chicken for $2. I don't think costco meat is that cheap, although admittedly I haven't looked in a while.