I found this interesting anomaly so I thought I would pass it on. I am renting a car at SFO for 4 days and used Costco travel to search for prices. Since I was doing a quick price check I put in the days of travel but used the default of noon for the pickup and dropoff times. The result was that Avis was the lowest price with about $220 for a fullsize car. So I was going to book it and since my flight arrives at 12:30 pm I changed the pickup and dropoff times to 1 pm. Much to my surprise the price jumped to $350 for Avis and they were not even close to the lowest price on Costco travel. Initially I thought I had just entered something wrong the first time so I went back and changed the time back to noon with the same days. Viola the price dropped back to about $220. So being an engineer I decided to try 12:30 pm with the result of $220 again. So how about 2 pm, back to $350.
So I don't know how to explain this but it seems odd that a half hour pickup/dropoff time change would result in $130 increase in rental price.