What happened to all the tube amps?

Answer is very simple...once you've owned a "great tube amp" there is never a need to sell it as you have reached audio nirvana.

i think what you are describing is a situation where many audio enthusiasts have been willing to try high end ss gear over the years as it has improved and the demand for the tube amps is therefore generally much smaller than ss gear. but i do not think that a 'vacuum' exists for quality tube amps. it is a matter of economics. i fear you have opened a can of worms here tho, so i'll be watching this thread for entertainment ;). btw i am no expert on tube amps but from what i read on this site there are lots of superb tube amps being produced still if you got the bucks.

330 tube amps for sale today on gon. None of them 'great' enough? I don't know.

Call Paul Weitizel at Tube Reserach Labs. They may still be willing to build you one of their $150,000 tube amps.
Is that great enough for you?

Last year at this time, there were MANY more to choose from, used that is. My Last monos were push Pull 300's X4. Sweet, Need more Current delivery. Only Have 10K now