Tricksy are the comparisons, they are.
I always get a bit antsy seeing various operating systems compared on "revenue generated". Really because it's a silly comparison. If you're a stockholder and only care about the numbers, then yes, revenue is interesting. You'd be talking about the companies involved, and less about their products.
But as a technologist, well, no, I don't care at all. It is not a useful measure of "success", of market share, in the world of applied computing. If anything, possibly the reverse. You can get amazing results with software that doesn't cost you a single currency unit, any unit. And if you're big enough, hey, paying for a couple beardy experts to keep the cheap stuff running might be just as cost effective as paying for a few more certified baseline chaps with platinum service contract hotline access to the not-so-cheap vendor. Alright, the former are harder to obtain, and even harder to retain, as you get bigger, but hey, you can try. Pick your poison.
What you should care about, as someone having to choose how to best support your business with kit and software, is utility. How much "compute" bang for the buck, the quid, the euro? If per-unit licences turn out to cost half elsewhere, then carrying double the amount of dosh to your fave vendor is nice for the vendor but means you migth be paying 100% more than you strictly need to.
So while the article paints an interesting picture, do be careful about just what you're comparing.