The other highlight note is that when Epic decided to shutdown Paragon, they opened up the refund offer for all purchases, not just really recent ones. They've taken essentially a complete loss on this entire project, that I believe had upwards of 100 developers working on it at one point.
But given Fortnite's success, plus the general solid padding of cash Epic always gets from having one of the most popular game engines that everyone else uses, means they can afford it.