I agree, $25K is a very high price. If I ever wanted to spend that much on speakers, there are others I would first consider. The KEF cabinets do measure nearly inert, and that is probably the main reason for the high cost.
I've heard the KEF LS50s, last summer. I like them. At the time I heard them, Ponzio & I spent some time comparing them to my small 2-way DIY CAOW1 speakers. They weren't identical, but both were equally satisfying to me. In general, I thought the CAOW1s had better mid range and treble dispersion creating a good image over a wider seating zone, and the LS50 had better bass response. I remember, in particular, how the LS50 cabinets seemed solid and quiet.
The price for new LS50s, about $1500, is 50% greater than the price for a new pair of Salk SoungSurround I speakers (about $900), which are essentially the same as my CAOW1s.
So, even the highly acclaimed LS50, is IMO not a real bargain.