I don't think auctions can be used to set values, cars tend to be individual because of things like condition, originality, numbers matching, owner history etc. I believe that the bottom line take away from the auctions is that the interest continues in Shelby cars from the era.
Look at Mopar they had their day in the sun, now other then Cuda's, 68/69 chargers, and wing cars their is little interest in them. As a whole fully restored correct cars are trading for less then 50% of their value from the mid 2000's.
Shelby even in death continues to draw a crowd.