What makes Telefunken tubes sound better?

I've reached the point in sampling 12AU7 tubes below $100 per tube where I'm having to buy tube crates to keep the pairs I've sampled. I've tried NOS and new, but out of all I end up back with Telefunkens as having the least distortion and fastest transient response. Yet the Telefunken internals are not the best materials/quality; NOS Mullard CV4003 or the new Gold Lions have higher build quality for materials and precision.

Are there links somewhere that talk to what is different for the internal design/construction of a Telefunken tube? I'd like to support newer tube manufacturers based on educated consumerism, and hope that we can get someone to replace Telefunken at an affordable cost before NOS stock is no longer an option.
The Germans have been absolutely anal, with regards to
materials, quality and engineering excellence, for a great
many decades. The notion that someone else's products(new or
old) could exceed their standards is laughable. I've tried a
number of other tubes, and would not consider any nine pin
miniatures, other than either(50's or early 60's) Siemens or
Teles. Right now; my CDP has six Siemens(grey shield) CCa's
in it. The proof is in the listening! Then again; there are
many out there that appreciate the colorations(ie:
warmth/tubiness) of other brands. To each their own.
Dunno! I've a box of other brands and they are all shadows of the Teles. Just replaced a set of JJ ECC803S (yeah,right) with old Dynaco branded Teles that I've had running for years in another preamp. Bang, bye bye JJ. Don't cryo. Amprex Bugle Boys are good too.
I might mention, as I have elsewhere; the EAT tubes are the
closest anyone has come, in recent years, to the quality of
the earlier products. But then the OP mentioned cost!