How to put a value on Aboriginal Art?

On reflection upon Art and Soul by Hetti Perkins, I was really intrigued by one topic that was brought up about how to value Aboriginal Art. Rover Thomas stated on the film that a painting that has a strong dreaming is a good painting, thus it should cost more. However, how does one judge if they paying the correct price for indigenous work if they do not understand the dreaming value. This brings me to another question, can we guarantee that the work we are viewing or purchasing is an authentic Aboriginal painting. According to my tutor there have been many situations in which Artists have been charged for fraud after producing works about non-authentic dreaming, or by artists that have not in fact created the work. It is also harder for non-indigenous people to determine whether the work is 100% authentic( including the context or the work) as to us, these works seem somewhat abstract without knowing the underlying context.