hmm, they're looking at being £150 minimum by the time you get them in the UK.
IF they sound as good as my NOS Brimars and Mullards and will last a lifetime, then 'maybe' I'd try one.
otoh, I have a lifetime stash of NOS ECC83s already of which half will most likely ever get used as NOS ECC83s last a long, long time. I've got 30+ year old amps that had original preamp valves in there that are still going strong. the quality of the old ECC83s was such that two complete sets of preamp valves are almost good for a lifetime of playing anyway.
The guy's idea is great, but the pricing is unrealistic to be practical for most players. If they came in at £30.00 each I think people would go for them, but that would mean far-eastern manufacture which the guy seems to be opposed to.