If you've never been to Costco then you don't know that everything is pretty much sold in bulk, that's why it's cheaper. Unless you're staying in a condo and you are a whole family, I don't really see where you would make use of all that you would buy. There are enough cheap places to eat and shop at if you take the time to do research. I have a lot of free time thus I have spent time on Zagat.com, visit-oahu.com, digital city hawaii.com, planethawaii.com,travelhawaii.com and lots of other sites whish recommend cheap and expensive restaurants, bargain activities and such. Don't think Costco would make it worth your while. Just my opinion.