While only the independently wealthy can actually afford to work for free, this essay does hit important truths.

For my entire career, the amount of pay I ask for a given position has been extremely elastic because the pay isn't the only form of compensation important to me. Among other things, if the position will expand my skillset in a way I want, or if it will get my name in front of a group of people I want to know about me, or even if it just seems like exceptionally fun and/or satisfying work, then my monetary ask is lower. Sometimes a lot lower, depending.

There is a floor below which I cannot afford to go, though.

I have personally found this to be an extremely beneficial approach in terms of my overall career arc (and, perhaps ironically, has dramatically increased the pay level I can successfully demand).