In general, all apps for Apple devices need to be downloaded through the App Store. You don't need to connect via iTunes as you can download directly over a wifi/mobile data connection (though of course you can use the iTunes route if you want to).
I am happy to pay for various apps that provide me with really useful functions that really help me day to day. There is a lot of expertise and effort that goes into making these things and the people that create, provide, maintain and improve them need to earn a living. I do use free apps too, but in general if I like and value an app I'm happy to pay for it. I was lucky in that I bought early for a one-off fee. Having said that they have done an enormous amount of work since and the app is massively more useful, powerful and customisable in its current form.
Now that they have moved to more of a subscription/in-app purchase model I would probably use part-free, with an occasional month of pro when I needed/wanted the extra functions