$50 - ouch! $15/week and 15 mins each way a day for me. An hour each way, I don't have the kind of time to waste on travel.
I wonder how long it would take to bike it the whole way though. hmmmm.
How far? city travel, depending on your bike, etc, I'd say estimate maybe 5-7 minutes per mile. Take a little time to scout some back road routes: quieter, nicer, safer. Get some flashing lights for your bike (cheap) if you'll be out real early or late. When the weather's nice, I'll go as far as about 10 miles on the bike to commute, but for me about 3 miles each way is roughly where the cost in time spent starts to outweight the benefits of bike vs car.