Had a situation a few weeks ago with a preamp tube in my rebel 20. Called everywhere in a 50 mile radius, lookin' for 1 lousy 12ax7 to no avail. Everybody I talked to had just "sold there last one" and were waiting for more to ship in. 
Meanwhile I twiddled my thumbs, pining away for my amp. Finally managed to find the "last Sovetek we got" at a little hole in the wall shop and $14.95 later I was up and running.
What I didn't realize though was that a couple of the shops I had called that didn't have any "NEW" tubes did have some used. One of them had literally a few hundred "USED" tubes. Needless to say, I hit the motherload at one shop. As it turns out they had about 3 large rubbermaid tubs FULL of used tubes. All shapes, sizes and makes. Granted, I had to separate the wheat from the chaf but I managed to come home with 2 extra sets of EL84's, (in this case SOVETEK's and JJ's, though there were many others), and about 6 - 12ax7's, and 3 ECC83's (SOVTEK's, JJ's, GT's & EH's), all which i only paid about 20 bucks for the bunch. All the tubes are in working order and about half of them appear to have been ripped right out of a brand new amp. Great way to be able to test drive some different tube flavors without having to spend a fortune although it does come with a bit of risk...I lucked out and with the exception of the one that I dropped on the pavement, they all work great. Moral of the story...never hurts to ask what your local shop has behind the counter or stuffed in a cabinet.
Meanwhile I twiddled my thumbs, pining away for my amp. Finally managed to find the "last Sovetek we got" at a little hole in the wall shop and $14.95 later I was up and running.
What I didn't realize though was that a couple of the shops I had called that didn't have any "NEW" tubes did have some used. One of them had literally a few hundred "USED" tubes. Needless to say, I hit the motherload at one shop. As it turns out they had about 3 large rubbermaid tubs FULL of used tubes. All shapes, sizes and makes. Granted, I had to separate the wheat from the chaf but I managed to come home with 2 extra sets of EL84's, (in this case SOVETEK's and JJ's, though there were many others), and about 6 - 12ax7's, and 3 ECC83's (SOVTEK's, JJ's, GT's & EH's), all which i only paid about 20 bucks for the bunch. All the tubes are in working order and about half of them appear to have been ripped right out of a brand new amp. Great way to be able to test drive some different tube flavors without having to spend a fortune although it does come with a bit of risk...I lucked out and with the exception of the one that I dropped on the pavement, they all work great. Moral of the story...never hurts to ask what your local shop has behind the counter or stuffed in a cabinet.