Especially in software industry, it's not that hard to arrange I believe. Even easier if we do it collectively. And when more and more people do it and it becomes a norm, the income will just readjust and return to the current levels.
But even today, when it's still not a norm, and I have a reduced income compared to my fulltime working peers, I still consider it a bargain. Extra free day is totally worth it. I am basically paying for some extra happiness.