I have read numerous debates about whether or not having a warehouse membership is worth the cost of joining. We actually have a membership to BJ's and Costco. I think that they are worth it.
I had a membership to Costco through my first employer. I found that there were several things that I liked to get there, so when I left that job and we moved to Richmond we got our own membership. We live less than 5 minutes from Costco.
BJ's just opened also less than 5 minutes away from us last winter. I found a coupon in the paper for a free day 60 day trial and thought I would give it a try. I actually compared prices with some of the things that I get from Costco on a regular basis. Some things were less expensive, some were about the same, and some were more expensive. I can't really say that surprised me. When it was about time for my 60 day trial card to expire Steve found out that his company was offering a discount membership for employees, and that we would be able to sign-up for 15 months at the 12 month price. I decided to keep the membership.
Which do I like better? They both are different. There are some items that are less expensive at BJ's or Costco - so I go there for that item. I do like that BJ's accepts manufacturer coupons and that their bulk sizes aren't as large. BJ's has Pampers diapers (Costco doesn't) so I figured I have saved the cost of membership by just buying diapers there. Both stores have a good selection of books, seasonal items, and clothes. They both also have a fuel center. Costco carries furniture and wall art, which I haven't seen at BJ's.
You may be surprised that the warehouse price may not be the least expensive price. I have found that things I used to swear by buying only at Costco, such as Chinet plates, paper towels, toilet paper, and laundry detergent, are actually less expensive if I pay attention to the sales cycles and match-up the sale with the coupon. It is also a lot easier to manage a container of laundry detergent that is for 32 loads than one that is for 132.
Both BJ's and Costco send out monthly coupon books to their members. I have recently found out that you can combine the coupons in the BJ's book with your manufacturer coupons. The other nice thing is that if the item is a multi-pack item you can use a manufacturer coupon for each item (that has a barcode) in that package. I have tested this several times and it works!
I think the bottom line is that you have to be aware of how much an item cost. When you are looking at warehouse prices you have to be aware of the unit price and what that unit is. Some items it is per pound, and some are by the ounce. It is also important to look at the item and make sure that you really will use it. The 144 packets of instant oatmeal, may not be worth the savings for you if you don't have the storage and you only eat oatmeal every once in a while.
I have read about several people who say that they share a membership with a friend or family member. That may be an option for you as well. I know that BJ's will let you shop there without a membership you just have to pay a fee. I also read somewhere (I don't remember where) that it is not unusual for BJ's to offer the free 60 day pass in the fall - so take advantage of it if you are interested in BJ's.
So, what do I normally buy at Costco or BJ's? It depends, right now BJ's has the lowest price on organic milk and on plain soy milk. I usually buy gas and diapers from a warehouse club. I don't buy lots of perishables from them, but I do usually buy baby carrots because that is a regular snack item at our house. I will shop at either place for food for church socials. I can find great deals on clothes at both places. (I went to BJ's last night and got 2 pairs of Levi's for myself for $24.) We bought our Wii at Costco and the games are reasonable at both places.
I think that what it all comes down to is that you can never go to one store (warehouse, mass merchandiser, grocery, drug, or department) to find the lowest prices on everything. You have to be willing and able to shop around and keep track of what size and price the item is in each individual store. Yes, it takes time to do that, but you will be surprised at how much you can save.