The first app that will be migrated to this system will be Octave, followed by others.
While this may be disappointing for some, I have realized that giving this work away free (as in $) doesn't serve your or my interests well. It is clear from users that they love what I have done, but want more features and better support. It bothers me significantly that I am not able to provide it because of time and money constraints. This will not be about making a lot of money, this will simply be about creating a better project by paying for developer time going forward.
By the way, if you have paid previously via the Play Store for any of my apps, no additional charge is required. Also, paying one amount will cover your usage of all of my apps, which will all adopt the same payment system.
How money is spent (after Google gets their cut):
10% (or more): Donated to Free or Open projects that my works is dependent on.
10% (or more): To the Lord's work (humanitarian work).
Remaining: Developer time
There is pretty much 0 overhead for the work I do.