Why is this screen protector so expensive? Is it a good idea to install one and if so can anyone recommend a cheaper one than BMW version?
I imagine that it's expensive because vendors think that's what the traffic will bear, as the expression goes, especially when brands such as BMW are involved.
In any event, per my brief research, if you're looking at the BMW part 77525A29255, that seems to list for $59, which also seems like the price that most Beemer dealers are charging.
Wunderlich USA has a version that costs a little less, i.e., its part 45195300, which goes for $35:
(Note that while that URL has R1250RT in it, if you enter your CE-04 model at Wunderlich and then do a search for Screen Protector, you'll wind up on the same page. That is, this protector appears to be used across multiple models, which all probably have the identical screen itself.)
I don't have a CE-04, but I did buy Wunderlich's product for my smaller screen, on my C 400 GT. I bought it to protect the screen from scratches and the elements. Have you priced out what a new TFT costs? On the C 400 GT, it's about a third of the cost of a new bike.
Good luck on your quest.