I am not sure, actual car values are going nuts. Its just that Sellers are.
Currently there are 17 actual CSL for sale, not M3 wannabe CSL's.. actual CSL.
Before the market became absurd, there were like 5 for sale.. at large.
Whats more interesting is, that they don't sell. There are Cars listed that have been for sale since roughly a year now. My guess is, that its mostly owners that don't really want to sell, unless someone buys it for their dream price.
Same with other "future classic" cars, 991 GT3 RS. Around 100 for sale currently.. barely any movement. Except for sellers reducing their prices.
Perhaps its different in the UK?