How expensive are best NOS tubes ? And how difficult to find ?

Phono stages, preamps and power amps. Any non-Chinese adequate substitutes? I know that if you have Lamm, Vladimir has a few sets of Russian tubes in stock for each particular unit, and it is not really expensive to retube them. But if you have, say, VAC or CAT or Atma-Sphere and want best longest lasting and most reliable tubes, what then ? Don't ask me why not Chinese, I can't talk about it here except that I don't trust their quality control.