Buy it once. It stays bought.

Valkyrie is a one-time purchase of $29.99, after a 14 day trial with nothing held back. No subscription, no account, no upsell inside the app. It runs on macOS 13 or later.

There is one exception worth stating plainly, because it belongs to a different app: Virtual Bracketing renders your keepers through your Huginn recipes, and that needs an active Huginn Pro subscription. Everything else here is covered by the $29.99.

Your files stay on your machine. The only network access Valkyrie has anywhere is reading your own recipes from your own iCloud account.