I recently acquired enough data to be able to say with confidence that my personal annual car costs, without biking involved, were approximately $3000. This year I saved over $500 in fuel by taking my bike as often as I did (annual fuel costs, without biking, is roughly $900 not including vacation road trips). Total spent going from no bike household to up and running on my current bike was a both embarassing and humbling $1400. Next year I've got a $200 budget for biking, and a $1500 budget for the car. The year after, I just get my bike budget.
My commute is twisted, it's 10 miles to the shuttle, or 37 miles to work. Both take about an hour and a half from front door to desk. I don't pay for parking, I don't have a car loan.
$340/month seems low. I'll trade your 1 mile bike commute for my 10 miles of hills any time One mile can't be far enough to get bored!