What's your valuation process for a higher value GA book? 0

[jabats]

What's your valuation process for a higher value GA book?

I am curious as to everyone's process to valuate a higher value (slabbed) GA book.

The data at GPAnalysis is thin on many of these books (e.g., Batman 1), and then I almost feel the sales data past 18 (or maybe 12) months ago is hardly relevant for the higher value / key books.

So my method is to basically extract 3 or so recent sales of books which are in relatively similar in condition, and try to broadly fill in the gaps (while also accounting for appreciation, which again for the keys seems like it can exceed 20% per annum (!) )

Just curious as to everyone's valuation methods... if they have different data sources, etc.

 

EDIT/NOTE: I apologize, I posted this thread in the wrong subforum. Please move it to the GA subforum if possible, with my apologies.

Edited March 14, 2017 by jahagans
EDIT/NOTE: I apologize, I posted this thread in the wrong subforum. Please move it to the GA subforum if possible, with my apologies.