ANY tube from the "Golden Age" of tube production (<1960) is going to command 2-to-10 times what a recent-production will. The higher the demand (and the fewer good examples left), the higher the cost. Hytron, General Electric, Syvania, and RCA were the four mfr's (at that point) that could produce tubes to JAN (Joint Army-Navy) standards. As time progressed, cold war tensions lessened, and transistorized equipment made its way into the military, JAN demands were made less strict. Hence, JAN is more meaningful if the tube is specified as being from the 40's/50's - (the $50 one is probably from the '70s).