Note: Prices mentioned in this article are valid in January 2020, and may be revised in the future. For accurate prices, please visit the correspondent product pages mentioned.
The short answer is that the cost for ARES Touch is "around 9€/$ per month" in Google Play or Apple Appstore. It is a monthly subscription that is automatically renewing and can be cancelled at any time. The price is rounded according specific guidelines (Apple likes for example to write 8.99 instead of 9.00) and currency conversion rates will further apply depending on your local currency so it is hard to make any general rule here.
This price may also vary from one country to another based on local purchasing power following the tables defined by Apple and Google. In any case the price is visible when users hit the Subscribe button in the stores.
When people install ARES Touch from Google Play or from Apple AppStore they start with the free mode that includes all the viewing, sharing and dimension features. This free mode can be used without any limit in time or file size but the other features are grayed out. Free users can subscribe at any time and subscribers can cancel their subscription at any time to return to the free mode if they want to.
The features "for subscribers only" include all the editing features and some premium annotation features such as Picture Note, Voice Note or Free Sketch. The properties palette allows free users to view properties while subscribers can also edit properties with this palette. Obviously the API is also not available in the Free mode.
Additionally, it is worth to mention that ARES Touch is included in the Annual Plan of ARES Commander sold 250€/$ per year or in the subscription of the Perpetual license of ARES Commander. In the case of the Perpetual license of ARES Commander, 1 year of ARES Touch and ARES Kudo are included. After 1 year the subscription of ARES Commander can be renewed for consecutive years and it includes also the access to ARES Touch and ARES Kudo.
To install or buy a subscription for ARES Touch, kindly visit the Google Play store (for Android) or Apple AppStore (for iPhone / iPad):