Don’t mind but the price according to the UI is high because Only features doesn’t decide the price your UI needs a lot improvement.
And don’t ask to users to decide your hardwork price. Decide by your own because you made it. Well for reference you can check others apps price on freelance websites. But keep in mind it’s not a android studio project demanded by majority devs.
You don’t have to add anything in UI. First clear your thoughts What exactly UI is and how it affects the User.
Learn basics of UI designing like color contrasts, Fonts, Sizes, Spaces, Backgrounds etc. You can refer the ready made UI’s on Dribble, Pinterest, Google etc.
Well, Okay but keep improved because it’s not a 1 Day game it takes too much time to understand these things, You use Cardview mostly and with white bg only so I don’t think you understand the concept of UI.
But Best Of Luck.