Psyonix has reported a stunning 15 million players supporting its indie hit Rocket League, a figure that very few indie titles have the ability to brag about. However, legend goes that the game originally became popular when it crept into the PlayStation Plus Instant Game Collection, and everyone realized how great it was after scooping it up for free.

With so many free downloads, we’ve always wondered how much the game has actually sold. In a recent interview with Forbes, the studio claims that it has sold 5 million copies across the PC, PlayStation 4, and Xbox One, and revenue from the game totals to a staggering $110 million.

Psyonix credits the continued success of  Rocket League to its DLC system, which only includes payments for cosmetic purposes. Vice President Jeremy Dunham explains:

Over time usually the player base gets smaller and smaller as more and more DLC is added to the environment, because fewer and fewer people are buying those items. Since we only sell cosmetic items and cars we aren’t cutting anyone out of the equation, and that’s why our numbers are actually going up month after month after month our active player base has been increasing for five months in a row.

Now, the follow-up. Where in the world can Psyonix go from here? Will it make Rocket League stuff forever, or will another game be in the works?