i am seeing this is true. very expensive.
thats why i might try to find an amp like WA22 that has the same tubes , but uses 6922 instead, i think i'd like that more.
5U4gs are expensive, i have a good variety to roll, and theres plenty more good ones out there to try out. i'm gonna try and buy a western electric 422A and a GEC U52 soon.
i think i have every 6AS7G thats decent except the WE421A which is on my to-buy list as well.
anyways, looks like to have a good stock means spending at least the price of the amp in tubes, if not more. depending on whether you want the best or just decent tubes.
Don't rush on the WE421A, but a good GEC U52 is nice. Don't get hung up on the GEC or the U52 bit however, there are some great examples that say neither that are identical ;)