Usually they bring about five thousand in good shape. They are not as
valuable as the triode units especially ones using WE 300s.
BTW there is no difference between a 300A and B except the position
of the locating pin which is irrelevant to any WE equipment that uses
them. In fact none of the ERPI amps even use the locating pin, that
was for the old 1920s sockets. They made the change to enable
interchange in a piece of telephone gear that was phased out well
before WWII. A bit of trivia. Non-WE tubes don't even have the
locating pin usually and no one misses it.