Hey, I've been aware of this difference for many years, but I don't understand 'why' it is what it is. Why are old/vintage 5AR4/GZ34 tubes so expensive, while newer production 5AR4 tubes are considered cheesy (performance/reliability) and very inexpensive? I think I can understand the opinion of the newer produiction tubes. All other octal rectifier tubes commonly used (5UG, 5Y3, 5V4, 5R4, etc.) seem to be reasonably priced as old production. What's up with the 5AR4/GZ34? Thanks!