I'd go to Maui, and search vrbo.com for condos and owner-rented properties.
I LOVE Maui, particularly the Ka'anapali side. (Notsomuch Kihei.)
If I was going back to Oahu, I second the recommendation for Kailua rather than Waikiki. :)
We're from AK, so prices don't seem that high to me, but it's all relative. Good luck with your decision and vacation planning!