I have the $100 a year executive membership that pays back 2% of your purchases annually. So far it pays back $150-180ish per year, so my membership is free and I'm also being paid $50-80 to shop there.
I had absolutely no problem getting the second card assigned to my dad who also shops there a lot. I get 2% of whatever he buys too...I think...I heard they were going to not pay the rebate on purchases made by the second card but I dont know if they followed through with that. Nobody asked me where he lived. I just said "Hi! Heres my card! This is my dad! I'd like him to have the second card!" and they gave it to him.
Some stuff is a very good deal. Frozen foods are incredibly cheap unless you get a sale and a coupon at another store. Seafood is ridiculously cheap...I get U10 scallops IQF there for around $10/lb. IQF lobster claws are $34/2lbs. Fresh wild salmon and Ahi tuna steaks are under $10/lb. Meat where I live is very inexpensive compared to the supermarkets. Vegetables are very cheap. Electronics are mediocre priced, but the return policy is very good. Clothes can be very inexpensive if you shop selectively. Some staples are no better priced than supermarkets with a sale.
The return policy is superb. Except for televisions, computers and a couple of other items you may return any item at any time for any reason for a full refund. You do not need your receipt...they have a purchasing history. If you are ever unhappy as a member, they will give you your membership fee back in full. Whenever I've returned something they've just asked if it was broken or defective and then handed me cash.
The return policy also works for items bought on costco.com. You may bring any purchase into a store and they'll hand back the item cost AND the shipping cost. Costco.com has a fabulous selection of really well made, attractive furniture at el cheapo furniture store prices. You may also purchase business services, travel, cars, insurance, banking services and all sorts of other interesting things at reduced rates.
I bought a watch there for my wife and a year later it broke, and I had trouble getting the manufacturer to take it back under warranty. I took it back and they handed me cash. I bought a set of costco pans, which were very good but after a year they discolored. I brought them in and they were aghast that they discolored and gave me my money back. I bought a vacuum cleaner there that started breaking belts and after the manufacturers warranty expired the manufacturer wanted me to buy a new belt every month on my own dime. I brought it in and told the returns lady the story and she said "NO! Give me that. I'll give you your money back and you can get something else!"
We also have a membership to Sams Club. I shop there sometimes because they're a lot less busy than Costco, have different stuff, and have some good prices on many items.
Many people find they can save the membership fee several times over just on one type of item or category. If you like fine wine or expensive cheese, Costco has a reallly good selection of both at bargain prices. Their Kirkland brand boozes are also a bargain. They sell a single malt bottled by Macallan, 18 year, for $60. The Macallan 18 year sells for $150+ in a regular store. They also have a range of Kirkland branded Bordeaux's and a huge selection of reds and whites. I can buy 2lbs of aged vintage cheddar for under $9. Ten pounds of chicken wings IQF sells for $12...half the price at the store. Rib eyes are $5.99 a lb and Porterhouse steaks are $5.68 a lb. A whole roasted chicken the size of your head is $5.99. A large pizza is $8.99-9.99. A 5lb tub of potato salad is around $4. A huge tub of organic salad greens is $3.65. The Kirkland brand dry dog food, which is pretty darn good stuff, is $16 for 40lbs. The organic human grade dry dog food is $19 for 25lbs. Hardcover books are very cheap if you're a book collector. Heck you can stop in there any day for lunch and enjoy a hot dog and a drink for $1.50, a huge pizza slice and a drink for $2.65 or any one of a half dozen other items for under $3.00. A frozen mocha or ice cream sundae covered with berries is around a buck. In the summer months the one near me hand dips ice cream bars in chocolate and nuts for $1.50. They roast their own coffee in a huge roaster in the back of the store...2.5lbs of yummy coffee thats still warm from the roaster is under $9.
So yeah, it can be a huge money saver and the days of buying things in 50 gallon drums are a little bit in the rear view mirror. If you're a single person the quantity can still be a little much but a couple can manage it fine and a family of 3 or 4 can manage no problem.