This is an interesting topic, this membership fee obliges you to buy from them as much as possible. So, the savings you make purchasing from Costco will reimburse the membership fee. So, the more you buy, the more you re-pay the membership fee. And yes, you have to purchase big quantities, not one pack of 10 toilet paper rools, but much more, not one small bag of rice but 20 lbs, etc.
On the other hand instead of going every week, going once a month for me, being single is enough.
Plus, there is something else, I would like to add, is that I have notice, in terms of quality and price, Costco offers more and more organic produces, fruites, vegetables, etc. at a competitive price.