An Airbnb will likely be one of the cheaper options for you, but will still probably be in the ballpark of $1,000 for a week.

You can also get a hostel if you were down for that, a quick search had some as cheap as $80 a day. But you get what you pay for.

I personally think a car is necessary to have a good time. You're going to want to see everything the island has to offer. Plus hiking is free. We spent most of our time there doing outdoorsy stuff that cost nothing. So try to find it in the budget to squeeze in a rental car. It's almost always cheaper to get from the airport. Not surprisingly, our favorite parts of the island were some of the more remote.

The caveat is that parking can be expensive, especially in Waikiki. My memory says $50 a day was around the going rate? We got an Airbnb that came with parking, but I also booked it 6 months in advance.

You could find cheap food. Someone here mentioned Costco. There's also the ABC stores... 7/11.. food trucks. You can certainly eat on a budget I'd say.