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iOS and macOS are separate purchases
"Tonaly" for iOS & iPad and "Tonaly Pro" macOS are two separate purchases.
The macOS app has additional features and all add-ons (in-app purchases) included by default. Also, it is a different platform that requires further development resources. That’s why it is a separate purchase – like a CD and a vinyl, where you don't expect to get the vinyl for free just because you bought the CD once.
Most apps that provide all apps on all platforms "for free" are apps with subscriptions – which would be, over time, way more expensive than this one-time purchase.