Estimate walking commute cost.
Walking is not literally free — shoes wear out and a commuter walking 800 miles a year gets through them faster — but the cost is small and entirely in footwear and weather gear. Set against the fare or driving cost it displaces, the net saving is usually the whole avoided amount minus a hundred-odd dollars. The time is the real currency: 1.6 miles each way at 3.1 mph is about 62 minutes a day, which is substantial unless you would otherwise be exercising anyway. That is the honest framing — walking to work trades commuting time for exercise time rather than adding to your day.
Walking Commute Cost
Daily minutes = one-way x 2 x 60 / walking speed; annual miles = one-way x 2 x days x 12; net saving = avoided cost per day x days x 12 - annual footwear cost
About 19 minutes at a brisk 3.1 mph, or 20-22 minutes at a comfortable pace. Uphill sections and crossings add more than people allow for.
Yes, close to the full amount of the fare or driving cost it replaces — footwear is typically 100-200 a year against a fare saving of a thousand or more for a daily commuter.