Certainly not realistic from an operational standpoint for sure. I think it just highlights the fact that many guitarists are stuck on myth, hype, old wives' tales, and marketing hoopla. There is a market for NOS tubes because it was created. I won't disagree that there are NOS tubes that sound better than modern production, but I certainly will not argue with anyone that there are modern production tubes that sound just as good. I.E. sound is subjective and NOS or modern production tube sound is more or less in the eye of the beholder.
NOS tubes of today cost all of 50 cents to purchase 50 some odd years ago!!! They were cheap run of the mill tubes then. Modern tubes are not inferior. Perhaps the only major difference between some tubes then and now is that then, there were military-grade tubes, and today there are not really many if any being reproduced. The question is if a military-grade tube is all that much better ( being 50 or so years old ) given the cost. The only way to find out is to purchase one and either be happy or disappointed.
The NOS tube market is kind of a sham really. Hey, there were thousands of these tubes NOBODY wanted stuffed in a warehouse, lets sell them to poor guitarists searching for the holy grail tone. How will we do that? We will tell them that these were made to a much better standard, that they sound way better, last longer, and then sell them for 1000 times what they originally cost!!!! Sweet, let's do eeeet!
The brass tacks are that a tube that has managed to survive 50+ years sitting, or even being lightly used was a good tube, to begin with. Where I have a big issue with the NOS market is the price and the associated buyer's confirmation that goes with it. Imagine you buy a NOS Tung-Sol ( add nausium to any tube maker you desire ) and it does give you " that sound ". You know there is not an unlimited supply of these tubes, so if you want to keep that sound for eternity, you must buy several more of that tube. So now you have $300 locked up in tubes that may or may not actually sound the same, but you have 5 or 6 or more of them laying around now. The only person that won was the guy who managed to snag a stockpile of essentially worthless tubes until the NOS market was born. There wasn't as much of a NOS market in the 80s and 90s until Groove Tubes came along and popularized it. Being one of the earliest rebranders and marketers helped them significantly. GT was founded in 1979, I got the GT Tube Amp Book in the 90s when I first started playing. So within 20 years, Aspen took tubes and vintage amps a long way. How do you sell tubes to people? You have to have an angle. GT became an OEM supplier of tubes, sold rebranded tubes, and sold the mystique of vintage amplification and the tubes to operate them.
I read a post today in fact on The Gear Page where a member was saying he will ONLY buy NOS tubes. Stating they sound better, and spank on modern production tubes sound. In the next sentence, he goes on to say that not all NOS tubes are good though, that you have to roll through several to find the good ones. Then the following sentence said that modern tubes don't necessarily sound bad, but just not as good as the good NOS tube you manage to find. This is what perpetuates the NOS market. You go out and buy a $50 12AX7, you like it ( for whatever reason ) and now you have to have as many as you can afford. You get a stash of them only to find out that half of them are microphonic, don't sound the same, or have some other performance deficiency compared to the one you really like. Hmmm, it kind of sounds like the same problem people have with modern production tubes. They don't sound a certain way, are too this or too that, yadda yadda.
I have several vintage tubes I snagged from my dad's stash many years ago. They don't sound any better than any modern tube I have. Oddly enough, the generic tubes that simply say Made In China, sound quite good in comparison. I tend towards JJ tubes for one major reason. They are the actual manufacturer of 1/3rd of the worlds tubes, they sound just fine and they don't cost stupid money for what was once a .50 cent tube.