Is this an option that exists or could be added in the future?
30% off would make the pricing feel less steep
That is a pretty recent policy, from the last year or two, it’s available in a limited number of countries, and it’s a pilot you need to manually apply for. And you still need to pay the fee to Google, it’s only reduced by 4%, so instead of 30 it’s 26 / instead of 15 it’s 11.
More info: Google Play Help Center: Enrolling in the user choice billing pilot