I've been speaking to a mate about this and it's unrealistic but a good point to bare in mind if it worked!
He reckon's that anyone (within reason) with a CSL for sale in the UK at least should club together and put a 10-15k premium on them, if everyone did it then it would move the overall price of them back up rather than just having one overpriced car, people then wouldn't have an option but to pay the inflated price as that would in time become the norm!...
As I say in the cold light of day unrealistic but a nice thought never the less, they'll go up in their own time, you only have to look at the E30 Evo's!