I think developers should try to get feedback from people who want promo codes.
As an example, in order for posters to receive a code, maybe you could ask them what's keeping them from getting off the fence so you know what might
be hurting your game from selling. Maybe it's something you could address in an update or your next game.
If you were to use the above example for RR, I would say the abstract visuals are what keeps me from buying. I'm not usually held back by graphics, as I value game play more than graphics. But with RR, it seems so abstract that it's difficult to tell what's going on or how the game flows. Then I read on the forum that some people were having a tough time grasping the game after the tutorial.
I hope all of that makes sense. I'm only trying to help out!