I've saved about $450 on gas alone in the past 6 months or so of commuting. Round that up to $1000 a year on gas savings and my bike and bike related purchases are easily paid off in 2-3 years. That is just gas savings not wear and tear. I am also much happier and healthier, which is much harder to put a dollar figure on. It does not take into account all the new bikes and equipment I want to buy now that I've started riding every day though.