8.3 mill player X 15 dollar a month = $124.5 million per month. Let's say you minus 20% for discounts, free 1 year when you buy D3....that's a min $112 mill per month (excluding the digital pets and mounts you can buy). Even after monthly expenses of admin, servers and IT Support, Blizzard still making a fair bit of money from this MMO.
That's not bad for a game that's more than 10 years old. I don't know the stats for DOTA.
I played WoW two years ago. Spent 8 months grind my character to lvl 85 and then stopped playing. It was fun with my friend. It was hard to form community. I like some of the older contents (Wraith of the Lich King expansion). After a while, it is just grinding for gears. I got bored from doing that. Starcraft 2 came out and I left the WoW scene