I know I enquired about a set a while ago and was glad I was sitting down when I heard the price.
Given the price these go for, I am surprised that there are not aftermarket reproductions of them available, that use modern valve gear and intake runner design.
Imagine a new version, that achieved the retro looks with improved performance. I have never seen a set in person and wonder if advancements in combustion chamber shape, valve seat geometry and port dimensions could not be applied. Add in some lighter weigh valves (which you are going to have to get made anyway unless they were a common ford part? I don't know.....) and they could potentially be a market. I presume you could design a remake around some of the newer off the shelf components.