Imagine this as a standalone iOS app and has no relation with the mac app, help me find the right price for it. (Don't worry, the final app is always a companion to your Mac app, not a standalone product)
Note: Don't overthink but also don't just pick the cheapest option.
* Unlike mac apps distributed outside of the AppStore, there is no easy way to implement Perpetual Fallback License for iOS. Charging a subscription is the only way to make this sustainable.
** If you're on the Premium tier, you can always unlock the iOS version for free if your license hasn't expired and you haven't activated all your 3 seats yet.