I am not sure when the term repair became a dirty word, but now it is cheaper to replace almost any item than to take it to a repair shop. They way the circuit boards are today you need a microscope, not a magnifying glass to look and see if a part got fried. How many people do you think understand ohm's law or what it even means, I myself would have to completely refresh my memory of it if I ever wanted to break out the non-existing oscilloscope and soldering iron, and I can't even remember what the thingy-ma-jig was called that was used to measure voltage current and wattage, (never mind It came to me now voltmeter I think). Things are just to small to solder, and then there is the problem of finding the right capacitor or resistor or semiconductor.
Tubes used to be so much easier, pull the blackened one, go to the grocery store, plug it in the tube tester, and see if it is bad, buy new one replace, and it worked, if it blew again after replacing then you took the TV or Stereo down to the repair shop because something was wrong.
We call them valves, and funny you say that, I pulled two old kt66's out the cupboard the other day, they cost pennies years ago, and after looking on evilbay they now sell for way over $100 each, happy days if ever I decide to sell them, good old GEC.
I guess I should have been saving tubes, they never cost much to replace, that's why they had tube testing machines in a lot of grocery stores here in the states. Less than a buck for most of them. I think they have gone up percentage wise more than the price of gold or silver.
Indeed they have, I just had a look on evilbay and $300 each is not out of place for a kt66.