[Nuthen]

Costco requires a yearly membership, so I think they are implying that the incentive is different. Costco has a strong incentive for you to leave with a decent time there, and feeling like you got a good deal (mostly through buying items in bulk) so you'll continue to renew your membership year after year.

At Walmart they might organize the store to get you to buy candy at the checkout line, or have a lot of less-than-healty options to tempt you near the essentials, to maximize the profit in that way. Because you're not shopping at Walmart because you want to be.

Disclaimer: I haven't been to Costco at a long time. And they still try to get you in their own way with free samples you can find all over the store.