I wonder what they sold for when new? $10? $15? They were replacement parts. Brent Jessee sells them for $999 a pair.
My experience with rare NOS tubes is very mixed. Sometimes great, sometimes indistinguishable from other good quality tubes. I'd have to own really great gear to consider burning up a thousand dollar pair of tubes.
One of my experiences with a rare tube was with RCA red base 5692, a 6SN7 equivalent. Sold by many tube sellers as a premium military low-noise 10,000 hour tube for $200-$300 each. Well, they do run for 10,000 hours if you run them at voltages well below a standard 6SN7 circuit. Running as a 6SN7 in a standard circuit there is nothing special about this tube at all. I had two of them for a 6SN7 shootout of about 20 different tubes. They tested perfectly and had no microphonics. Soundwise I ranked them in the middle of the pack. They were decent and sounded good, just nothing special. I sold them as I had no use for them and others were willing to pay good money.
