Locus Map Pro can be purchased on Google Play Store or Amazon Appstore. Also, the in-app purchases in the Locus Store are processed by the services of these vendors. Both Google and Amazon have their own individual terms of purchase. The accepted payment methods vary according to the country of the purchase:
Unfortunately, Amazon stopped communicating effectively with us a few months ago so we are not able to upload updates on it. Locus Map Pro is available here in version 3.45. Amazon also stopped supporting some devices.
Google and Amazon accounts are not connected so purchase on one of them can't be swapped or otherwise transferred to the other. Whatsmore, Amazon policy of All Sales Final means no refunds in case you want to return the purchased app.
Google provides up to a one-year money-back guarantee.