Hi Remie,
Welcome to the Anvil forums! As well as the syntax fix, you probably want to modify your code to get your input from a text box on the web page, and display the output on the web page too!
Here’s a link to a fully worked example - it doesn’t do price calculations, but it does get the user’s input from a TextBox component, process it with Python, and display the result on a Label component: https://anvil.works/ide#template:hello_world
The start of the video here shows how you could build this kind of app. (It then goes on to show lots of more advanced features, which you can learn all about from our other video tutorials).