You doing anything special to get these prices? I am going to Denver the beginning of March and the cheapest prices on hotwire.com are like $24 per day for economy cars. I checked on prices a while back and could not find anything cheaper than this.
Nothing special. Pickup from Denver airport. I was just messing around with it and noticed what you're talking about with the prices in March which are much higher. It may be because they increased prices in anticipation of Spring Breakers or just because it's within a certain amount of days (last minute planning). I plan my trips well in advance and never had a problem getting the $16.95 rate. If you plug in dates in April, you'll see what I'm talking about.