We have developed a psychological game based on art psychotherapy (according to shapes and colors we show how your unconscious brain is working trough 5 dimensions on a daily/weekly and monthly basis) with the aim to help people to understand and discover themselves on more deeply level.
Well done for creating the app. Great question.
Regarding setting the price: I would try run a survey with some screen shots that show the game and it's purpose/experience, and ask potential users how much they would pay. I would run one survey with open end questions, such as: "which payment method would you prefer? Answers: one time payment, download payment, monthly payments, yearly payments....
and "How much would you be willing to pay for the service - in each of the various payment options".
Then, I'd run another survey with the same questions, but provide various options for them to choose from. There is a lot of psychology behind the way the questions are done, so it is important to do them correctly.
Once you've done these survey's, you'll have a better understanding of what you users are willing to pay, and how. Also, if you do the survey right, you could collect potential first clients (they would leave their email address and you can notify them when you launch).
I've successfully helped over 350 entrepreneurs, startups and businesses, and I would be happy to help you. After scheduling a call, please send me some background information so that I can prepare in advance - thus giving you maximum value for your money. Take a look at the great reviews I’ve received: https://clarity.fm/assafben-david