I can buy applications for my devices in play.google.com using my desktop browser, then those app automatically installed on my device.
Now I would like to buy the professional version of Car Scanner (which named Car Scanner Pro).
The app offers in-app purchase, but I would prefer to use my desktop browser. There is no such app in the play.google.com Car Scanner Pro.
Question
Is there any way to accomplish the in app purchase via play.google.com using my desktop browser?
As far as I know there is no web-based interface for performing in-app purchases.
In-app purchases are only triggered by the app.
The only chance to purchase an in-app item on your computer would be to use an Android emulator with PlayStore installed (Google provides images with PlayStore) assuming that the app you want to purchase items in is available for x86 devices (the emulator is not an ARM device).
In this case you could set-up the emulator with your Google account, download the app, start the app and purchase what you want from inside the app.
Q & A