People don't consider the costs when producing something like that. You can get hydrogen from electrolysis and nitrogen from the air. However, you need to buy the equipment, run it, maintain it, and have a place where you store it. None of that is free. I suppose your labor is free if you don't value your free time at all. I can see doing it as a hobby, but to save money? Perhaps if you don't have a job, want to keep your costs down, and live off the grid, it's an option. I've seen videos where people generate a decent amount of electricity from a creek, and to be able to get fuel from that is kinda neat.