While softwares are scalable. Problem is that you not the owner of those softwares, will you be able to negotiate with your employees to give you 1-10% of the total profit they generate. Unlikely! Yes, software developers make a lot of money but they still end up in category of "expense" not revenue generator in accounting. You'll only get paid what it costs to replace you.
You need to start a business where you own total upside and total downside. It's high risk and high reward game, if you get lucky - you'll be in the names like Bezos.
Having worked with software developers, they hesitate from charging too much as they don't understand the value of the work they are providing and are generally happy making stable amount of money over lifetime.
This is not bad if you value stability. But if you want more, you need to play with fire. Highly likely you'll get burnt but that's what it takes.
I quit my job to produce 3d printing filament and I am making 7000 euros a month as the business grows, I'll probably make more but see it's a limited scope process to make filament so it's very scalable. I expect upside to increase steadily over few years before I plateau and then I plan to move on to another opportunity.
Here's my project:
https://medium.com/endless-filament/make-your-filament-at-ho...
Just like me, pick a problem where people have money to pay and start finding how how to reduce costs and increase sales.
In business/sales/marketing you need to display confidence which often software developers lack (because they know of so many ways things can go wrong). Customer doesn't like this, customer wants to feel that your solution is flawless without any holes! That's where clever sales person come and sell the software solution for several multiples of what it costs to make it.
When you've enough money, you don't need to struggle - you need to do things that are fun for you and have upside.