When NBA 2K18 launched in September, it had more ways than ever for players to spend money inside the game. That business model is working, with spending on microtransactions, downloadable content, and season passes jumping 57 percent year-over-year for the NBA 2K series.

Publisher 2K Games, a subsidiary of Take-Two Interactive, revealed that it has sold more than 6 million copies of NBA 2K18 into retail. It notes that sell-in as well as sell-through to consumers have both grown over 20 percent compared to NBA 2K17. In its quarterly earnings report, Take-Two also highlighted that the basketball game also had significantly more people purchase and download it digitally relative to past games.

Overall, NBA 2K18 is bringing in more players than ever, and those fans are more engaged.

“To date, total users and average daily users of NBA 2K18 on current generation platforms is up nearly 30 percent over last year’s release,” reads Take-Two’s quarterly report. “We believe that NBA 2K18 will become our most successful sports title ever, both in terms of units sold and recurrent consumer spending.”

Recurrent consumer spending refers to sales of any virtual currency, add-on content, or microtransactions. Sales of those digital items have fueled the success of Grand Theft Auto V and its GTA Online mode since 2013, and now Take-Two is filtering the model down into its other releases, like NBA 2K18.

That business model is important because it enables 2K to unlock the value of its most engaged consumers and biggest fans. Those players would like to spend more money on their favorite games, and GTA Online and now NBA 2K18 enable those players to spend almost an unlimited amount.

“Recurrent consumer spending grew 66 percent year-over-year and accounted for 48 percent of total net revenue,” reads Take-Two’s report. “The largest contributors to net revenue in fiscal second quarter 2018 were NBA 2K17, Grand Theft Auto Online and Grand Theft Auto V, WWE SuperCard and WWE 2K17, and XCOM 2.”