If these tubes were indeed "steel" tubes they would be a lot cheaper. But I doubt there is much steel in them at all. They are made on ceramic, Aluminum, silver, tungston, and no doubt a host of other rare metals. And there is a brand new 8877 on ebay right now for 550. You just have to know how to shop. Just like I found a 572b exactly the same as the Taylor from RF parts for 39 bucks each.
Rich
Rich
They are rightfully called external anode ceramic based vacuum tubes. This is because the anode, or plate, is not contained inside the vacuum but rather outside of it to allow for better cooling. The "steel" part of the tube is silver plated copper and nothing more.The copper allows better heat transfer and the silver plating allows a better electrical path as silver is a better conductor than copper and even silver oxide is better than oxidized copper.