I stay there annually in a timeshare unit and buy groceries at Foodland at Ala Moana since I don't rent a car. The prices aren't much more than I pay in Chicago, at least for what I buy. You can get a free Makia card to get the sale prices. I always walk there and take a taxi back since I buy more than I can carry. With a tip, the taxi is about $10.
You might want to check prices at the ABC store. Although prices are higher than the grocery store, sometimes a sale is cheaper. But grocery items are limited.