I just went to Sam's Club the other day because I needed to restock something that were easier to get there. It's funny that I haven't been there in a long time, and not since really focusing on our budget. I did take a set amount of money to spend in there and did pretty well--good thing I had a calculator, I would totally overspent! I did notice a few things though that I hadn't fully been aware of before being so conscience of how much we are spending.
Some of my observations:
1. It's not ALWAYS cheaper to buy products at warehouse stores
-The reason I know this is because most of the things they have are name brand, often times the generic version of those things cost less at the store even without being in bulk or on sale. (Of course this depends on where you shop, but for Walmart generic brand, this was true).
-Sometimes it is the same price as the store, but you have the benefit of getting it all in one large package, but don't confuse this with it costing less.
2. There are less choices to chose from
-Most of these stores only carry a few brands or packaging options for the things you'd like to get. Which can often times limit your use for them or how you'd like to store them.
3. It's easy to overspend
It's SOO easy to add things to your cart in those stores and not think it'll add up to much, especially if you're used to the grocery store pricing. After putting 3 things in my cart I was already close to $25! You really have to pay attention to budget and the prices there. If it's something you don't NEED to have in bulk or could get for cheaper at the grocery store, it makes more sense to put it off and stock up on your own price terms.
All that being said, I'm still a huge fan of these stores, because there are things that really are cheaper there. I've just become aware of somethings to keep in mind as I shop! :) If you don't have a membership currently, I wouldn't say it's a necessary thing unless you have some things in mind you know you'd use it for. If it's just for groceries, you can definitely do the stock up thing for less at your local stores watching their ads and buying generic brands.