Edit: IAP may sounds like a good idea, but I have not had a good experience with on the Mac App Store. It’s a lot of work to get it right and conversion rates are really poor. I make more money selling apps that require an initial purchase than through IAP. Maybe that means my apps suck and those who try it on the App Store, don’t find it to be worth the money… Except that it is not the case with apps on my site, where I also offer a free trial.
Regarding desktop apps for both macOS and Windows:
In my case I sell 90% outside the Appstore and 10% in the AppStore (for the same app).
As Sam noted rightly, it does require more work (and that goes with limitations too) to make it acceptable for Apple.
Also, the verification process is something frustrating. Sometimes you get rejections for silly reasons that gets approved the next time you submit the same code. Figures.
Anyhow, if you are new to selling software, your best bet would be start outside the App Store or Windows Store.
What I do recommend is to use in-app buying. Don’t just point to your website for the payment procedure. Put that all in your app. Sales will be much better this way (mine sales doubled when I implemented this).
I use Paddle for this - it’s incredible easy to implement this in your app.
In my experience, selling on a platform such as the App Store or the Windows Store, once pass the frustrating reviewers, is much easier, since you immediately get the traction of the platform.
However, outside of the platforms, you don’t pay the 30% fee, and you don’t have to put up with the crazy reviewers. But you must build momentum for your web site. I found https://appvisor.com to be valuable. If you have a free, evaluation version, iAP or not, they can make sure it is posted to the hundreds of software repositories.