Cost is lower on some items, higher on others. If you really really want to save some cash, watch coupons and ads as you will get better prices at other retailers.
The worst part of costco is customer service....there is none. If you call the optical dept you are on hold for ever and my wife and I tried to load a heavy item and were struggling to get it on the cart. Costco employee walked right by and never even offered to help, even after we pointed out that we could use help.
Support your local business's and pay a little more, at least you get customer service and the money stays in the community.