After having read three articles that mentioned nothing about Microsoft having charged for the update, I was wondering whose sources were more credible.
Hmmm... I wonder if you maybe saw an incorrectly referenced mention of the fact that when Microsoft dropped support for (I think it was) XP they did offer continued support - at what I assume was a hefty fee - to major corporate/institutional users.
"Worried about WannaCry attacking your legacy Windows XP business computers? Worry no more! We have a fix! For only $100 in bitcoin we will send you an executable to run on your..."