We're going to Maui the two weeks before our Kauai trip and when I first booked my rental car it was $680 for a compact car for two weeks. That was eight months ago. The price has been dropping and in the last week I was able to reserve an intermediate car for $343 for two weeks through Costco. That's a great deal and I'll keep watching all the way to when we pick up the car.
I'm getting ready for my next visit to the Pono Kai. I arrive on 12-13 and I have had a reservation through Discount Hawaii Car rental for months at $205 total. I just checked on the Costco website and I was able to book $130 total. I don't expect to beat this price but I will be checking all the way to departure. The nice thing about these reservations is as soon as you get a better rate book it and the cancel the higher one. You don't have to pay or give your credit card until you pickup the car. I'll be in Maui the two weeks before and my rate there is $380 total for the two weeks. I'm thinking this could drop another $25 to $80.
Make sure you book early when you are going during any busy times of the year especially during holidays.
Jeff & Kim Silvers