There seems to be little question that the market price goes down with age. But I tell you this, the BEST (OK, boy there's a term that varies widely in it's definition),,, the BEST replica's I've seen are in fact many older versions. I recall a stunning Contemporary here on island a few years back. Webers, accurate detailing, just the right amount of "bling". Whew, don't see many like that anymore. But such a build was reasonably common a decade or so ago. Back then the ONLY people that could get in the Cobra game had deep pockets, even a common brand would set you back a $100K. Side oiler of course! Not much after market stuff around, you had to improvise.
Today it's fairly easy for a lot more folks to get into the Cobra scene. Far less money required now than then. Copies being cranked out on a daily basis, modern this that blah blah. Well, OK, so we have a new ball game then. And I have a deeper appreciation for the "old school" replica's myself.
There are some VERY NICE true to original spec replica's or Shelby's built today, and like "back then" it still costs a bunch to get there. If you want the very best, bring a big wallet!