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

@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.

@samiamnot- Not exactly, "serial numbers"(though some use the term), as that would be specific to just one tube. Typically, date codes indicate a week, month, year and sometimes a location/plant, for every tube in that time frame’s run. Your seller can probably provide more data, for your specific tubes. https://www.tubemuseum.org/SearchResults.asp?Cat=24 6922s are dual triode(two separate circuit/channel) tubes, like most other, commonly used for audio, miniatures & octals. Basically, two tubes in one. The closer the measurements(hence, "gain"), between two separate, paired tubes, the closer your channel balance will be, when listening. Regarding tubes in a push/pull circuit; one wants the individual triodes balanced, to achieve the most accurate(least distorted) sine wave(signal) reproduction.