My guess is you're aquiring most (80%) of your users through cross promotion? I'm super curious to know how many new users to your network you get, and what channels they come through.
Our strategy/priority on acquiring users into a game is, in order, - platform featuring - in-app cross promotion - affiliated devs/pubs cross promotion - social channel promotion - organic installs
In his book, Amir Rajan, developer of "A Dark Room", "A Noble Circle" talks about the get rich slowly method of having several premium games that are very much targeted to small subsets of gamers and slowly growing your stable of well crafted games that get a handful of downloads each per day. The hope is that each grow organically and maybe even self-cross promote. If you'd care to weigh in, I'd be interested to hear your stance on that theory in terms of being a solo/premium only dev.
This is true in a few genres such as hardcore historical military strategy games, point and click adventure games, etc which have passionate fanbases that recognize and are prepared to pay for quality but are often under served.
