Last night after dinner Sarah and I calculated how much it costs us to take her car one mile.  We started with the original purchase price of her car, added in all the maintenance costs (oil changes, tire rotations, lubes, new tires, etc.) that have been paid on the car, added in all the gas costs, added in all the insurance costs, and then added in all the repair costs (we didn't include registration and tax costs).  Then, we divided that figure by the number of miles on the car.  We learned that it costs approximately $0.40 to drive her car one-mile.  We then figured out how much it costs me to bike one mile on either of my bicycles.  Again, we started with the original purchase price, and then I added in things like tubes, chains, and additional eq.  We then divided this figure by the number of miles ridden on each bike (this was easy for my new bike because it has a speedometer and odometer).  My new bike, after fourteen months of ownership, costs me about $0.34 per mile to ride.  However, extrapolating costs and mileage three years into the future (to get a reliable figure to compare with the costs of Sarah's car which is four years old) brings the estimated cost per mile of my new bike down to $0.14 per mile.  A complete guesstimate for the cost per mile to operate my old bike is something like $0.025 per mile.  Using these figures, we then determined that it costs me $10.46 to get to work and back every day (14 miles * $0.34/mile + $6.00 in ferry tickets).  If I drove to work (using Sarah's car, for example) it would cost a minimum of $16.00 per day (approx. 20 miles * $0.40 per mile + $2.00 bridge toll + $6.00 absolute minimum for parking). Of course, these figures are not absolute.  For instance, I save $30-$50/month by not having to enroll in a gym to get exercise.  My health care costs are probably lower because my body is generally in better shape than if I wasn't biking.  Also, my overall stress level is lower because I don't have to fight traffic and I can burn off any stress by merely biking harder until the stress is gone and nothing but exhaustion remains. What prompted this was a discussion I had with one of my coworkers.  The co-worker's significant other was thinking of buying a $1,000+ mountain bike that would be ridden something like six times a year.  If you assume that each ride would be something like 20 miles in length, then in the first year (assuming that the SO did not replace and chains, tubes, tires, seats or other parts and didn't spend any money on helmets, gear, or clothing), it would cost the SO $8.34 per mile to own that bike.  Given that, it would probably make sense for the SO to buy a used bike (which can be gotten at a deep discount compared to new bikes) and ride that.  However, the lure of new will probably overpower the SO's common sense.  Oh well.