I thought that too, but at 7500 miles that comes to a bit under $1000, and I've probably spent that. $350 for the bike, but then racks, several LED lights that lasted a while and broke, ditto tail lights, a set of fenders that I snapped, a new set, rack, now an HID light, about $40 in chains, another $30 in brake pads, about $250 in clothing (alert shirts, rain jacket, shoes, socks, underarmor, winter layers, gloves, a couple of helmets, PSolarX balaclava that saves me in the winter, etc), $100 in studded tires, another $50 to replace the original crappy tires at 5000 miles this summer with race lites, frame pump, panniers ($25 Nashbar sale), at least $60 in various mirrors I've tried, $60 for parts to build a new rear wheel to replace the crappy one the bike came with, probably a few other things.

Now, a lot of that was initial layout. I'm still going through chains and brake pads, and I had a spate of beginning-of-dark-commuting light problems this week, but I'm not buying new frame pumps, racks, panniers, or clothes. So though I think 13 cents a mile is a pretty good number now, it's going down constantly.

However, I think it's probably driven up by people who, though they don't spend much, don't go very many miles a year either. And also by people who buy $2500 bikes to commute 3 miles (I have seen a couple).