Was looking at setting up rental car for Hawaii. ( Costco site)
One week rental beginning at Noon was $100 more than for a one week rental beginning at 1:30PM.
Accidentally discovered the difference when I adjusted the pick up time to fit with my flight arrival time. The default time is 'Noon", on the Costco site.
If a rental rate looks ugly expensive, you may want to try adjusting the pick up time to see if it makes a difference, assuming you have a bit of flexibility in your schedule