My costs over 1 year and 5000 miles of commuting: Bike, $300. 3 Tires and 3 tubes, $70. Upgrades - stem, handlebar and bar-ends, $50. Waterbottles, pump and computer, $50. That's about $470, and really that's it.

In savings we ditched one car, which would have been about $500 in gas and insurance alone over the same period. Figure in repairs and that's where it really looks good - I could replace my whole bike for another $300-400, but there's not much you can do to a car that's that cheap.