Digital research firm Superdata says Blizzard's collectible card game Hearthstone pulls in an astonishing $20 million per month—per month!—which according to VentureBeat is even more than the also ridiculously popular (and lucrative) Dota 2.

The summary of the report, which examines the state of the CCG genre in 2015 and beyond, compares Hearthstone to World of Warcraft in the way it "transformed" the genre. "Blizzard’s first digital card game has deep mechanics, but it is more accessible and streamlined than long-running games like Magic: The Gathering," it says. "History repeats itself here: In 2004, World of WarCraft became the MMO to beat thanks to a combination of the popular WarCraft IP and gameplay that was more accessible than existing MMOs."

The Dota 2 comparison may be a bit out of date, as the numbers are based on a report from March, and Hearthstone remains far behind the real big dog in the pack, League of Legends, which in October of last year was on pace to earn more than $1 billion in 2014. But it's still an awfully big money truck that's pulling up every month, and given Hearthstone's relative newness—the mobile version, which boosted monthly revenues by 31 percent, only came out in April—it's almost certain to grow considerably.

I guess there's some truth to what they say about "free-to-play" being "pay-to-win": Hearthstone players are paying, and at 20 million bucks a month, Blizzard is very much winning. The game's coffers are set to grow further this month with the release (exact date still unconfirmed) of The Grand Tournament, a new expansion comprising 132 cards. You can read our recent interview with game director Eric Dodds here and check out the cards revealed so far here.