If tube manufacturing could include lithium refining, Elon Musk might invest in it.
I am surprised that wealthy guitarists and big amp makers haven't invested in a tube factory; only EHX who purchased a Russian tube maker under their New Sensor Corporation, and now the export ban makes it impossible.
Mexico seems like a great location for a tube factory IMO. Wonder if any tube amp makers actually did a cost/value analysis on it; I'm sure the upfront costs including bribes to Mexican government officials are cost prohibitive... maybe the drug cartels would be interested, great way for them to launder their money, like the US is doing in Ukraine.