I fully agree with you: the GoldenPass Panoramic line offers some magnificent winter scenery. To travel through the snow landscape is truly a wonderful experience.

On the Zweisimmen-Montreux leg I also had this particular 1st class car with VIP seats.
However those VIP seats did not require any extra cost. Maybe I was just lucky (the train was nearly empty), maybe it was due to the fact that they were "backwards" seats i.e. not in the direction of travel.