I remember reading a an article that stated that most upper middle class people have a Costco membership. Essentially, it is a warehouse with high quality bulk products at a reduced cost. I have been inside a Costco many times in the past. There are certainly some items that are definitely worth the savings, especially the non perishable items. However; I have to say that I have not had the best experience with the produce in particular or the frozen food items.
I bought organic spinach and within a few days, I began to see more than half the amount wilt. The avocados never ripened so the entire bag was a waste. I bought frozen chicken kebabs and followed the instructions, but they never fully cooked during the time recommended so they were cold inside and required further heating. An acquaintance of mine discovered her frozen treat had mold all over it.
Based on my experience, it is best to stick to the non-perishable items at Costco!