I think it's good value for money especially if you're after the older ages. I must admit right away that I'm not a member (yet). That's mainly because they don't ship bottles to Denmark. But being in Scotland every summer, that's not a very good argument
I visited the Vaults once as a guest, and my host let me buy two bottles. However my wife couldn't get access in her wheelchair, so then I used that excuse for not joining.
I'll soon have to give up and join since they are now rebuilding the place and installing a lift