Money doesn't bring happiness, but what we buy with money should.
That being said, I feel like a lot of players are complaining about the value of their monthly subscription (content offered/$).
While at first glance the only solution would seem to be “churning out more content,” there are other ways to increase the value of a subscription (think Amazon Prime: video, twitch, music, books, online storage...).
FFXIV offered ingame items based on the number of monthly payments paid (these items are now offered with achievement points), and SE was not starving because of it.
Therefore my suggestion is to offer a certain percentage of cashback that can be used for purchases in the online store (for example $3 for every month paid).
What do you think?