In a new post, Forged Chaos outlines some of the preliminary details of its pay model, although the developer allows for enough wiggle room in case of changed minds. As it stands, Trials of Ascension will be playable as a one-time purchase, although adding on a monthly subscription (30 days of which is included in the box) opens up more races, the discovery of innovations, and the ability to be a lord, lady, king, or queen. The team is also "considering" a skill cap for non-subbers. A loyalty program will reward faithful subscribers with fun goodies like a treasure map and t-shirt.
There will be other ways for you to spend some dough in Trials of Ascension, including purchasing Writs of Time, acquiring permanent race access, and making a custom crest.
[Thanks to Android for the tip!]