Rental car rates will def depend on what car you get too. We booked through rentalcars(.com) with Alamo but checked with Costco and they had a better deal and a larger car which was an intermediate with
Avis (discount included a free weekday plus 25% off base rates). We picked up at the airport (the taxes and fees were nearly $70) too.
We also booked 5-6months in advance as well.
If you include the added day on the rental car that could not get any discounts added our total cost for 10 1/2 days worth was just over $254.00 (extra non-discounted time was over $56 by itself).
Obviously that's not a price you could count on but still.