Been Costco members for over 20 years and since the executive membership became available, our rebate every year is at least double the membership cost and usually 3-4 times as much. Long lines there don't bother me because they move fast due to scanners that work and employees that know their jobs. $20+/hour gets a better employee than you will ever see at Walmart, where the standard for employment seems to be a pulse.
Some amazing deals can be had there too. For many years, I had been intrigued by kamado cookers, but was never going to spend more than $1,000 on a glorified flower pot. Well, a couple years ago, I was in our Costco and they had a large, good looking kamado for $599. Figured I'd research it when I got home, which I did, and found positive feedback so I thought I'd take a closer look next visit. Went back and was checking it out when I looked up to see a $200 discount. Ended up with a kamado right between a large and XL Big Green Egg for $399, with cart and cover!