Is it common for tubes to outweigh the cost of the amp or preamp?

When I bought my grey shield/plate, early Sixties, Siemens, they were just over $250 a pair(average). My CDP takes six, in it’s analog section. The player’s original cost was just under $5000, so I wasn’t upside down. The diff was remarkable, so- I bought six more, for spares. After about ten years, I thought I might compare the spares to the used. No apparent/appreciable difference (boy, was I glad!). I’m hoping the CDP will outlive me. You apparently enjoy the clean, wide open, extended sound of the CCa’s. If you’re ever in the market for 6SN7 types, the bottom gettered, 1940’s era, Sylvanias and Ken-Rads, offer the same presentation and are very close to the performance of such as the Tung-Sol round plate, or Sylvania 6SN7W(tall bottle/metal base). Much less expensive than them, too. 

Just for anyone who is interested, there is a difference between shields and plates. All Siemens 6922/E88CC have gray plates. They made a chrome plate 12AU7 and you can’t mistake these, but as far as I know they never made chrome plate 6922s.

What the gray shields are are two vertical strips located beneath the getter supports where the supports attach to the top mica. The gray shields look just like the gray plates.

Siemens 6922/E88CC made after 1964 or 65 or so have silver shields and gray plates. A silver shield can be seen on the tube on the left in the picture in this ad from ebay. The M in Siemens is printed right over the top of the silver shield.

https://www.ebay.com/itm/E88CC-CCa-6922-6DJ8-Siemens-Matched-PAIR-NEW-NOS-SILVER-SHIELD-Strong-/182403712807

Why care? Back when I was buying tubes it was said that the gray shields were a far superior tube to the silver shields. The silver shields were described as being bright and sounded terrible compared to the gray shields. Even CCas come with either gray or silver shields.

Opinions change as stocks of the most desirable tubes disappear, though. Silver shields may be considered good quality tubes now. I don’t know. Anyway, if you’re buying Siemens 6922s you should know that there’s a difference between gray and silver shields.

@samiamnot I'm glad you're happy with your new tubes!Check back from time to time on the ugly tubes if you're curious to try something different sometime without investing $$$.Enjoy!

@tomcy6 - Also of note- The silver shields all had an internal, stamped date code. All the early, grey shields, had screened, external date codes. I can attest to the(slight) brightness of the silver shielded Siemens. They’re not bad, just not CCa’s. I’m certain; they would sound beautiful, in a lot of systems. Still have a great pair of middle Sixties E188CC’s(silver), just in case.

@rodman99999 Are date codes kind of like serial numbers for tubes?

My new tubes are date codes 262990 and 262928. I don't know the significance of the codes but I assume it's good that they're close in number.

They're also rated:
16.8mA/15.8mA & 15.8mA/15.8mA

I don't know what those milliamp ratings actually refer too. I'm a total newb her. Still learning.