Air is abundant enough that humans need not consider it's costs when taking their next breath.
But like clean air is/was analogous to the abundant fruit tree in the comic I posted. And it TURNED INTO polluted air through people ruining it just like the fruit BECAME non-free when Og claimed it and made others work to get any.
"No free lunch" is an aphorism used by people who don't want to let there be free lunches. It's not inherently true.