Why price "premium" features for an already priced app?

This application really is great for education, but I do not think that we need to have priced premium features because this app is already priced. It would make a lot of sense if either both the application were free and the premium features were not priced or both the application were priced and and the premium features were not priced. It must be one way or the other and not both.

It is a great application, and it ought to be reliable about its information, but it is just expensive, but, then again, the app did cost only one dollar, so I guess that I can settle with either two or three dollars for the premium features.

Drivingforfun365 about Morse-It