Compare transit and bike commute costs.
Both options here are essentially fixed costs, which makes the comparison unusually clean: a transit pass is a flat monthly charge, and a bike is a capital item with modest consumables. Neither varies much with how far you travel, so the distance matters less than you might expect — it determines cost per mile, not total cost. On these defaults, cycling saves about 550 dollars a year. What the numbers omit is weather and reliability: most bike commuters keep some transit access for winter and bad days, so the honest comparison is often cycling plus occasional single fares against a full pass.
Transit vs Bike Cost
Transit annual = monthly pass x 12; cycling annual = annualised bike cost + gear; saving = transit - cycling; cost per mile = cycling annual / annual commute miles
Typically 400-800 a year against an 80-100 monthly pass, once the bike is amortised. The payback on the bike itself is usually under six months of pass savings.
Many cyclists do for winter and wet days, but pay-as-you-go single fares are usually cheaper than a full pass if you only need them 20-30% of the time.