My first year of commuting was like around $500. It wasn't until I got the bug and rode more and bought more "higher end" stuff that I hit over the $1,000 mark. I still believe my bicycle commuting is costing less than insurance, maintenance, fuel, taxes, license fees etc (environmental overhead for the vehicle) etc... Plus my health is even better. I have made tons of friends over the past few years! Gas keeps going up and down and I don't really pay attention!
Keep Cycling!