The problem with Costco, of course, is the large sizes of most of the items. I think it's worth it for many items - produce, meat, seafood, soda (a case - 24 cans - of Diet Coke will be about $6.89 at Costco, while a 12 pack will cost that much at the store unless you hit a sale), milk, ice cream (Mochi Ice Cream - yum - $6.00 for a six pack at the store, $9.49 for a 18-pack at Costco). You'll save big bucks on many items. BTW, you'll also save about 15 cents a gallon on gasoline.

I try, also, to get as much as I can at Safeway (and get the UA miles w/ the grocery card). I buy a strofoam cooler and a bag of ice to keep cold things cold for the trip back from Kapa'a (Safeway) or Lihue (Costco) to Poipu).

I'm in the enviable position, however, of being able to store non-perishables when I leave. BTW, I give perishables to the neighbors (a nice family lives next door full time).