You're right on that. There's no way an audiophile will be able to get their hands on a master tape. Maybe there's a rare exception, buy I've never heard of it.
The term most of us use is Master dub and It is indeed possible to get them.
Examples are The Tape Project, Yarlung Records and the German audiophile society. At one time all of them offered master dubs, perhaps some still do.
I have tapes from each of these sources, some are extraordinary.