You can share a costco membership with 2 people. I share it with my mom, we get the executive membership that's $100 a year - but at the end of the year you get a 2% or so rebate on what you've spent... that usually ends up being about $75 or so for us.

I think it's worth it - I get prescriptions there, tires, food, etc. When you get tires there, they do nitrogen refills & free rotation, so every so often when i'm at costco - I give them the keys as I go in to do that. electronics are ocassionally a good deal. i get prescription glasses & sunglasses there... They have a selection of organic foods that are good prices for organic foods. A 5 lb bag of organic spinach for $5 is hard to beat. It does mean I'm eating lots of salads until it starts to go bad, then I make a big pot of spinach soup.