I thought you explained it perfectly yourself, but sure. You were not addressing the original point about breathable air being free. Instead, you built a straw man, based on the presumed cost of /breathing/ it, which actually had nothing to do with the original point.
By the way, if you want to be as anal about the definition of "free" as to include totally peripheral expenses (as if a pencil costs you $100 for signing a check with it), you might as well get to the bottom of it and say that everything is free on the basis that no matter or energy is ever expended.
