According to a new report in the Wall Street Journal, Nintendo has at least started to intervene in order to prevent disproportional amounts of in-game transactions in the titles it has licensed to Android and iOS developers. This may reflect the increasing drive to regulate such charges, which can lead to significant profits as a result of using free apps.
https://www.notebookcheck.net/Nintendo-asks-its-mobile-gaming-partners-to-reign-in-their-microtransactions.413230.0.html