Its not android-like push notifications or anything sophisticated as you're currently imagining, rather a simple background task (on the bottom right taskwindow)that updates the .list file and checks for updates every given time and sets the application on the foreground with an orange flash on the taskbar. My mistake calling it push but its som
It can't be themed (for now) as the main idea is to create a minimal auto-updater.
I won't explain how versioning works, but I can reveal its SHA256 based
I don't consider the price high, I personally maintain a medium sized server that makes multiples of this price tag within a week from the donations.
Reasons of "high price"
Considered as premium software
Its based on pure win32 (Not MFC, QT or some shitty WPF crap)
Its compatible with all windows versions bigger or equal to win2000
Native Code: Most routines written in C with a custom C++ win32 wrapper for win forms
Statically linked hence highly portable (400-500KB size)
100% x86 Native executable (Native C++ forms are rare today)