To take the CTA in Chicago would cost me $4/day. I paid about $1750 for my dream commuter. I need to ride about 437 days to pay it off. Assuming two weeks vacation, there are 250 commuting days a year (50 weeks times 5). Accounting for winter (when I ride less though I still ride) and other factors, I easily commute 175 days per year (probably closer to 200 but let's keep it conservative).

I will pay off my bike in 2.5 years.