Don't be fooled by price and packaging. I use the very best "NOS" (sometimes used ones, that test like new) that cost me less than you'd imagine:
Raytheon 12AX7A black-plate/halo-getter $8-$10 ea.
RCA 12AX7 black-plate for $10-15 ea.
RCA 12AX7 long gray-plate/square-getter for $1 (super lucky!)
GE 6681 for $17 ea.
Ken-Rad 12AX7 black-plate for $18 ea.
RFT ECC83 for $6-$12 ea.
Telefunken smooth-plate ECC83 less than $20 ea.
Tungsram ECC83 for $12-$15 ea.
Okay, I confess, I once spent up to $45 ea. for one of my favorites: Mullard long-plate/halo-getter 12AX7. But that's the most I've ever paid (I've gotten several for less than $20 ea.), and I've only been buying in the last five years.
My point is that if you learn what you're looking for, you can get it for less. Learn to identify the tubes, make sure they're properly tested, and shop around. Don't pay a premium for pristine paint/logo or boxes. Sure, you can pay A LOT, but you don't have to.
Oh, and don't buy that b.s. about amps being "designed around current-production tubes." You can always make a good amp sound better, to you, by optimizing it with better quality tubes. Can you imagine what kind of amp would have been designed for Ei tubes - a disposable one?
- T