Book value is unimportant when it comes to older, scarce highly desirable cars.
My 325iS had a book value of R27k & I cant think under which circumstances I would have sold it for that amount (I got a tad bit more than that btw).
My cuz has a German Spec, I have a more door & I am good friends with Fiekie M3 (check his thread somewhere on Fanatics) & neither of us would let our cars ever go for book.
I think to find a neat E36 M3, be prepared to pay in the R100k region...kays & condition dependent of course
As they say, & it so true when it comes to these cars: "Goedkoop is duur koop"