I have solved a lot of practical problems with a Pi. It is a really nice computer for controlling things around us.
A few money generating things:
I have used it for years to control lights and sound for theater plays. This saves lots of money as you don't need to hire a technician for the show.
I used to sell DiscoHAT's for this purpose.
A cart burning PiHAT for creating new retro games. I have written two new games for the Atari Lynx 30-year anniversary. The Pi can both cross-compile the code for the Atari Lynx and it can burn the carts. It is even possible to control a 3D printer with a Pi for creating the cart covers.
Two of these games are mine "Find a way to my heart" and "On Duty". Selling them at retro festivals like PRGE and eJagfest bring in much more money that just selling the Pi used to create the games.
You could also learn to use the Pi in industrial settings for gathering data or controlling something. I am occasionally using Pi's for catching flaws in industrial systems.
So the Pi is a tool like a hammer, a screwdriver or a magic wand. You can use it to generate something amazing that generates money for you if you have what it takes to learn to use it.