What makes a tube amplifier so expensive? The tube itself, the mains transformer? The output transformer? Looking at the price now to build a 10W tube audio amplifer one could purchase nearly an entire entry level home theatre system. 25 years ago one could purchase one tube which could dissipate 1Kw for about 300U$ – in those days, that was. Tube amplifiers are still very much in demand in the music industry – especially for guitar amplifiers.
That been said I was very pleasantly surprised by an advertisment I came across through Google, a company by the name of Tube Depot or www.tubedepot.com selling tubes at a very good price and in most cases they can supply a potential buyer with a matched pair. And you can get transformers at very reasonable prices as well. Make a turn there and see what you think.