As someone who wrote Indie Windows software, it's not only the problem of supply vs. demand (I'd actually argue that there are a fair amount of people who are happy to pay Coda-levels of money for software), the biggest problem is marketing.

If you're an Indie macOS or iOS dev, you've got so many places to drum up news about your app. If you're on Windows? There's Windows Central, and a few smaller blogs (and Reddit, but rules against self-promotion in most subs mean you're very likely to get your post whacked). Promotion is a huge challenge for Windows desktop devs