There is nothing wrong in wanting to feed our families.
If I wanted to profit, I would stop selling digital versions of our books and only do printed versions. The last time we did that was for Two Scoops of Django 1.6, which made more than 1.5, 1.8, and 1.11 combined. That's the only way to put a halt to digital piracy: don't sell digital works. But that denies people in a lot of places access to our works. And means we're about pedagogy over profit.
We give hundreds of unpaid hours per year to open source projects. For years, every single book we've released we've given hundreds of print copies away as charity. Through books, articles, and open source contributions we have furthered people's knowledge around the world for over a decade.
All this means we're running a charity for the Python and Django community. These live classes are our means to hopefully do open source work for a living, with a few classes per month to cover our bills.
Can we make more money building apps for other people? Absolutely