Also, we're talking about a game that makes 16,5k/month MINIMUM...
Okay, I stand corrected, they may not be paying, they probably be just followers.
It would actually be crazy if the Adult Games Industry would be pulling those kind of numbers. But sadly no, truth is only the biggest games like Summertime Saga and BADIK make that amount of money.
The rest of the creators make it rather for the love of the game, than for money. Since its so hard to get exposure and support, and since most games are available for free anyway.
And as it was already correctly identified followers isn't the same as paying members.