Costco is legit, and a huge saver if you have a larger family to feed and supply. They have fantastic deals on produce, paper goods. toiletries, and certain groceries. Their meat department is solid with some exceptional buys to be found. Good selection and prices on electronics. We have also caught deals on outdoor furniture, landscaping, plants/ shrubs, and even local gift cards to restaurants and attractions. I've heard their automotive/tire center is worth shopping, but I have not used them before.
Additionally, they have an annual cash back program for platinum members.