I assume that you are sure it is truly NOS, even if it is ANOS I think you got it at a very reasonable price.
I wish I could find some GEC tubes for that kind of money or something reasonable.
I notice that there are some sellers who know the 'pain price' for some of their stuff. They price the tubes at a point where you just can't justify buying them. There are also the truly silly high price, obviously ridiculous, that makes you ask, ala John McEnroe, "you cant be serious" !
I can only speak for myself but when you see the same high priced tubes being offered over and over you would think that the seller will cut the price. Sometimes they just don't. Are they using the old sales technique that car dealers use like putting the convertible sports car in the showroom to just get people looking?
I took a chance as it was advertised as untested and that is probably why I got it at the low price. Gauging it against the sound of the Mullard it is a little woolly in the lows and not as clear or engaging, but that was how the Mullard sounded with little hours on it. For that reason I have a good feeling about how the GEC will blossom with further hours. It certainly doesn't sound like I have bought a plum.
I have seen a dealer selling these for £75 on ebay and in my eyes that is greedy.