Many people I say no. Obviously costco's marketing machine has suckered in a lot of people here. It works on an averaging basis. It charges a bit less for products, but you have the membership yearly fee. If you don't spend much, you lose. if you spend a lot, you win. You can't honestly believe that they are able to get things for cheaper than walmart, so they're making money somewhere, and it's with that membership fee combined with people buying a lot of crap they normally wouldn't "to save money". Plus the membership fee encourages "forced loyalty". I've seen the prices, and for our family it still wouldn't even break even on the $40 (or whatever it is)/year.
It's really quite cultish as well. I don't care for costco at all.