Well, if you are buying name-brand products like shampoo, many food items, toiletries, etc... then the answer is NO. I have comparison-shopped numerous times and found the prices to be exactly the same as if I bought 40 rolls of toilet paper at the regular store. However, if you buy the Kirkland or Sam's Choice brand, sometimes you will find them to be cheaper.
Where CAN you save at these stores?
1) Dairy - For instance, a 2-lb. block of cheese is $5.35. At the grocery store, a 1-lb. block of cheese is $4.99 or higher. Milk and eggs are also cheaper.
2) Bread and Tortillas - You can get 2 loaves of whole-wheat bread for $3.99, whereas you might pay $2.99 for one loaf at the store. You can also get 36 tortillas for $2.65.
3) Meat - If you need to buy meat in bulk, this is the place to go. I love Foster Farms chicken, but it is $5.99 a lb. for chicken breast at Ralphs or Albertsons. It is only $2.99 a lb. here, with the breasts packaged separately, which I love!
4) Laundry Detergent and other household items (store brand). It is nice to have a 3-month supply of laundry detergent, but you'll probably only save money if you use the store brand.
I know there are many other great deals at these stores on books, clothes, electronics, etc.... so I'm mainly talking about Food Shopping.
The bottom line, though, is that if you don't have the money in your budget to spend $10 on 8 rolls of paper towels, then don't do it. Go to the .99 cent store and buy what you need for 2 weeks, and spend only $2. Don't go over your budget because you *think* you are saving money. You don't need to buy 5 months worth of shampoo if you don't have the money right now. Stay within your budget and don't get lured into the temptation of thinking"if I buy it at Costco, I am saving money!"