I see them listed from $200-$400, so that $75 version must be a beater.
I think it was a limited printing by the Munger family with no plans to print again soon I have been told. I remember I got my copy when they first came out for under $25.
Swinehart and Massey books' prices have also skyrocketed with their limited printing. Others have too.
I suppose rare and popular books are like rare and popular bows, huh?