If we assume 1960, a matched pair of EL34 would run $115.45 today according to the CPI inflation calc, so 10x is not far off at all.
Incidentally I can buy matched quads of EL34 for less than that today. Thats kind of why I don't put a lot of stock in the notion that tube gear makers ran stuff hard because tubes were cheap to replace years ago. The dollar number is low, but as a percentage of hourly rate they were more expensive 60 years ago than today.