IMO, restoration cost and the lack of true restoration expertise has, and will continue to ultimately hold these back from becoming big investment quality cars. Mainly the expertise. Unlike other marques/models (think Gullwing, 73 911 RS, M3 EVO etc... , it's my opinion (worth exactly 3.5 cents) that CSL specific knowledge is too closely guarded by the true cogniscenti which muddies the water with new, wealthy, younger investors looking at potential additions to their collections. Everyone has an opinion on what's correct or not and it's frustrating. BMW's lack of any records on options etc is another significant factor in repressing the values. I mean I own one and still find it difficult to get straight answers half the time!