To be honest, all things being equal, I can't see why the 507 is worth a £10-15k+ premium over a PPP. Same engine, but you get a fancy bonnet and decals.
I can almost understand the premium of the black series, it has fundamental chassis/bodywork/suspension changes etc. But IMHO it's not double the car compared to a PPP/507, but it's double the price.
According to how many left , there’s only 10 C63 Black Series in the uk and 5 sorn so only a total of 15 cars left , I think the BS will rocket in value at some point.