Let’s call them window sliders

Charging $125 for a window “kit” when all you need are the sliders is highway robbery!

In my experience it's not just the sliders and not even primarily the sliders (the white plastic pieces), it's the flocked piece that goes around the edge of the glass that seals the glass to the frame. Without it the wind just always whistles right there in front of you next to your left ear. You aren't going to make those on a 3D printer.