If you go to a Sam's Club with a Costco within @15mi they will have lower prices than a 'non Costco' Sam's Club. They are directly competing with Costo and will have the same or lower prices.
And yes Sam's/Walmart can buy and sell at a higher volumes than Costco is capable of.
Not true here. My two clubs are two blocks apart and only occasionally will I find items cheaper at Sam's, even then it's only pennies.
These stores do so much volume, that the manufacturers cater to them with exclusives in packaging to avoid just this problem.
Cameras will come bundled with a case and a memory card that are not offered anywhere else. I buy a cereal that is identical but is packaged in different weights in both Sam's and Costco. There are electronics like phones that are packaged exclusively for Circuit City or Best Buy.
With discount stores offering price guarantees, they are anxious for manufacturers to offer them 'exclusives' so they know that no one can compete against them in price with an item, because no one else has it. Sometimes it's nothing more than the color of an item, but it's a different stock number, so it is not subject to a price guarantee with a competitor.
On another note, Costco carries fewer items than Sam's which results in higher sales on those fewer items. Items that don't consistently produce high numbers aren't kept. You don't see the amount of discounted merchandise at Costco that you do at Sam's.
I have much more confidence in Costco's non major branded items than I do in Sam's. Their own brands (laundry detergent, dishwasher detergent, etc,) are not relabeled majors, instead they are made exclusively for Costco and are required to be at least as good as the majors. You'll often see their products in Consumer Reports as Best Buys.
The caliber of employees (at least at my local clubs) is definitely a notch higher than Sam's. Overall, I think that Costco is a better run organization and their return / customer satisfaction policy is second to none.
This is not a put down to Sam's. I love the WalMart/Sam's success story and I shop at both. I just don't see the 'big guy', 'little guy' comparison as telling an accurate story.
I think that it's smart that both stores try not to have the exact same brands while still offering similar products for sale.
In addition to the Eneloops that Costco carries, they also have their own brand of alkalines (Kirkland) in AA and AAA sizes that have consistently received excellent reviews.