Earlier quoted context omitted.
Unfortunately, as of September of last year, Google Play's terms and conditions match Apple's App Store's terms and conditions, in that apps must use Google's payment method and cannot advertise or include links to alternate methods of paying for the app or distributing it. Ultimately, these policies are meant to further restrict viability of competition by either company.
Just a few days ago Google announced that you could use Spotify's payment method as an alternative to Google play. The top-rated HN comment for that article was: "As a user, why would I choose this?"[0] Competition only works if the competition is effective enough to change user habits. For the average person not educated in monopolies or tech regulation, is there any incentive for them to switch to paying Spotify in…
If it's 30% cheaper, that may be enough of an incentive. Though I don't know if that's the case here or if Spotify just eats the fee when you pay through Google.