I've seen quite a few people complain about the high cost of cycling as a hobby. Sure if you want the latest carbon frames, you're going to pay for it. But a bike for commuting can be had quite cheap. Witness the old gray mare.
Bike $35 used.
Fenders free discarded by friend when he upgraded
Panniers $40 on ebay
Handlebars $9.99 Nashbar
So we're looking at a total cost of $85 for this bike. My best estimation is that I have something like 5,000 miles on this one so that's roughly 1.7 cents per mile. I would call that a bargain.