I don't think of "carfree" itself as having a cost. But transportation costs money, and the cost will of course be different for people that drive cars versus those that don't. I ride my bicycle for nearly all my transportation. But some of it is mass transit. Some of it is walking.
I also frequently take long (5 miles at a time) walks on the weekend for pleasure. Does that have a cost? I suppose, the cost of the food to fuel the walk. But is that a cost really? If I didn't exercise as much then I might have more medical problems as a result. How do you figure out cost, when each item you're trying to quantify has a cost of NOT doing it?
I spend about $750/year on cycle-specific clothes and bicycle parts. I'm sure I could trim that but I don't feel motivated to. I spend about $500/year on mass transit.