Are all of these NOS tube inventories real? How have we not consumed them already?

Depends on the dealer.

Oh yes we have consumed it long ago, what remains as NOS even NIB (different thing) is any surplus from the 80’s for military use and most likely for the non popular ones. Otherwise term NOS is catchy and a good trap. That does not mean that a used tube is no good but is silly to pay as NOS. Still some collections will surely have gems and hunting them down is fun.
G

I recently bought a small lot on the evil site, mainly for the Sylvania Type 80 (ST enclosure) for the princely sum of $12.94 including tax and shipping.

I’m pretty sure it is NOS, and it is a STUNNING rectifier in my Zen Amp.

What I usually look for is a reliable seller who knows how to test tubes and includes all relevant measurements.

NOS has NOT been consumed.

I'm new to tubes.  Where's a reliable place to find Tungsram PCC88 / 7DJ8's