Ebay price on 801a is still a viable price though, since Chinese 300b’s are weighty price wyse.
I guess the choice depends on more than just current price. If you intend to use a amplifier for a period of time (say 10 years), you have to consider the availability and price of valves for that amp and that period. Picking a valve that is currently in production is likely to be a better bet than a valve that is not made anymore. Of course it may be a valve that is not made anymore that no one else is using, so not always that simple. I saw elsewhere today, someone commenting that they were finding it hard to find pcc88's anymore. perfect example of this. What was a good choice 5 years ago looks less good now.
The same argument can and is made for solid state devices, in a way its even worst as it can be harder to find parts from 5 years ago than a valve from 80 years ago, but the difference is that if used in their SOA the lifetime of SS is in effect longer than our own so less of a problem.
Reminds me, I have eight vt4c's sitting in a pair of broken amps here that I should put on ebay sometime.
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.