I agree with most of what Richard says on Urban Space but not that he doesn't save money by biking everywhere. Here was my comment:
Even if you get all of your repairs done at the shop, it's still cheaper to bike than drive or metro. The GAO estimates the operating cost of a bicycle at $0.05/mile. The average car operating cost is $0.26/mile. Shady Grove to Franconia-Springfield is about 25 miles and will cost you at least $0.09/mile and no one rides it that far.