I question whether it's cheaper;  definitely not faster.  I take 48 minutes on avg to bike a 30 min drive commute.  But it is healthier and a good way to cut gasoline usage. 
  
  
In a way, you are still saving time b/c you don't have to spend as much time working out. I think you are coming out ahead no matter what   
  
yes true.  This way I get a 1:45 min cardio workout (round trip) twice a week.  If I drove, I'd spend another 1:30 per day getting to and from a gym with a 1 hr cardio workout staring at some dude's fat ass in front of me in a hot stuffy room.  In short, more cardio, less road rage, less hot, smelly, boring gyms. 
  
And I need all the cardio I can get so I can haul my old, fat ass up glaciers.