Has anyone made an reasonable income from the app or Mac store?
Apple. 
I’ve dabbled with the App Store.
From your sale price, Tax is deducted, and Apple take 30%
Its always been peanuts for me compared to selling direct, but direct is a lot of work, and relies on year after year of web site exposure.
A new website and a new app… you get more exposure in these stores because people go looking…
I do receive a good income from the Mac App Store, but I have now 15 apps there, and a few of them successful enough to sell several a day. I did start in 2013, and at the time, it was much more profitable. But still today, it is good business.
I had great hope for the Windows Store, but I have to confess that to this day, it does way less than the MAS. The same apps (I don’t have all of them on both platforms) sell between 4 and 5 times less.
If I was to advise one, I would say MAS, if you have apps that can cater to the general public.
The Windows Store is at the moment more trouble than it is worth, IMHO.
Is this only due to the lack of revenue, or other reasons too?
I have a couple of apps in the Windows Store and am about to add another, so am curious about your comment.
Between the Mac App Store and the Windows Store, the Mac App Store is a clear winner overall.
Wasn’t really selling much at the Windows store as my customers seems to prefer buying off my own website. So much so that it didn’t hit the sales numbers which Microsoft wanted and they just took those apps out of the store suddenly and disable any updates for them.
One thing good is that they don’t tie you exclusively to selling at their sales platform and you can sell your apps concurrently at your own website
Making a reasonable income on App Stores (iOS, Mac, Windows) is tricky (as a solo developer) but possible.
You should look at the recording of my XDC presentation in Denver for some insights on mastering the Apple app stores.
[quote=426757:@David Cox]Is this only due to the lack of revenue, or other reasons too?
I have a couple of apps in the Windows Store and am about to add another, so am curious about your comment.[/quote]
I have been in the Windows Store ever since Windows 10 reached users. My constant observation has been much less sales than in the MAS.
I put apps there as a spin off of my usual development, rather than as programs I would have created especially for it.