The best cost/mile ratio for a new bike I've seen was CigTech's Denali, which cost him ~$159 from WalMart. Before selling it, he had at least 14,200 miles on it (as of 12/08), which worked out to 1.1c/mile.

How much have your commuter bikes cost per mile? For simplicity, include only the cost of the bike itself (no accessories, no repairs). If your bike was free, that's great. You can still give your mileage.

OK, I'll start. Bike name, purchase price, miles traveled, and cost/mile (divide cost by miles).

Forge CTS 1000 - $395, 540 miles, 73c/mile.
Jamis Coda - $560, 667 miles, 84c/mile.
Murray Milestone - $20, 8.5 miles, $2.35/mile.