No insurance, minimal maintance, low acquisition cost, no fuel cost, no registration, no gridlock, gets you outdoor time and exercise time while also commuting.
Not only low cost to the user, but municipalities who implement cycling infrastructure also save money in the long run due to lowered healthcare costs, road maintenance costs, etc.
Turns out a 3 foot wide bike lane that handles loads of 200-400lbs is a lot cheaper to maintain than a 6-8 foot wide lane that handles 2000-10,000 lbs. Who could have guessed that????