Talk to people. Literally anything that can save people money or effort is worth doing, no matter how niche.
I just spent the morning building a tool that can probably save me and all of my friends hundreds of dollars per year, simply because I asked and gathered information. That scales up!
Besides finding out if anyone actually is willing to pay for your solution, I think it also makes the problem bigger for you.
The advice is often to just scratch your own itch but, to be honest, my problems aren't that big to justify the many hours I'd have to put into automating them, for example. I can usually find a workaround or just live with the problem, no biggie. But if more people have the problem, then suddenly the impact is greater which may provide more motivation for certain people.
I just spent the morning building a tool that can probably save me and all of my friends hundreds of dollars per year, simply because I asked and gathered information. That scales up!