The disparity of the prices for MkIVs on the one hand and the Cobras newly built by Shelby, Kirkham, etc on the other hand is even more astonishing taking into account that the Shelby cars named by Constant in his earlier post have bodies made of plastic, not aluminium.
I believe that by and large the buyers of MkIVs and the buyers of new Shelbys etc belong to two different groups (with certain overlaps, of course). The MkIV buyers are basically vintage car aficionados who do care about originality and who would also consider buying a classic Jaguar, Lancia, or Porsche, while the Shelby continuation car community is more focused on cars that are 'powerful and sexy' without having too much regard to history. In line with this I would guess that the MkIV prices will follow the general trend of classic car prices which will not necessarily be true for the Shelbys and the Kirkhams, let alone the kit cars. As is well-known the prices of classic cars have been going up for years and are largely expected to go up further for reasons discussed above. In Germany we have a 'vintage car price index' which was established in 1988, it comprises 88 models of 7 countries. Since the year 2000 this index has risen, on average, at a an annual rate of 6%, it did not collapse during the financial crisis in 2008/2009. So I am confident that the MkIV owners will not lose money on their cars in the years to come, although prices may not continue the 'meteoric rise' pointed out by Mark in the post starting this thread.
Jürgen