How much does Actions for Obsidian cost?
The app is free to download from the App Store. There is a 14 day trial period. After the trial period, the Shortcuts actions will trigger "Please buy" reminder dialogs.
A license removes these reminders.
You can choose one of three price levels depending on how much you think is fair: "S" (€11 / $9), "M" (€14 / $12), and "L" (€17 / $15). These licenses differ in nothing but the price.
It's an experiment in fairness, basically. For example, I hope that if you use Actions for Obsidian in a commercial setting, you consider buying the "L" license. Or even if it's for personal use, and you feel it makes you 5× as productive, you might select something else than the "S" level. It's entirely up to you, though.