The task of putting a value on any book is not an easy one. There are many Idriess books sold that have far exceeded the valuations that we have entered in our Bibliography.
We have based our valuation on:
Rarity or scarceness
Past Sales at Auction and known prices paid at Bookdealers and in online auctions such as eBay.
General economic cycle and other influences
We have tried to value all the books based on the condition that a collector would appreciate, so that 'Very Good' means a book that is complete and original, still reasonably fresh in appearance, shows some small signs of wear, and has all its pages with no tears.
Whilst foxing to pages is a reasonable expectation in older titles, evidence of damp is not.
Owners names, booksellers info, and dedications are acceptable.
The Dustwrappers, if applicable, should also be complete although some tears or small parts missing may be acceptable.
A book that is ex-library, damaged by damp, or reconditioned is generally not acceptable as being in 'Very Good' condition.
Scarce titles will always command a premium even if they are not in 'Very Good' condition.
Some titles were meant to be used out 'in the field' and most likely suffered as a result (Cyaniding for Gold for example). Others had limited print runs or were issued during the war years and thus became lost or severely damaged (Guerilla Series for example).
Past Sales at Auction and at Bookdealers
We have tried to smooth out the higher and lower than normal prices paid. Generally, we have ignored the prices paid that we know have far exceeded the usual price paid. Similarly, a book that sold for far less than usual has also been excluded.
Some of us have been collecting Idriess for decades and have made it a life-time hobby.
Economic Cycle and Other Influences
Generally, prices paid follow a cycle in tandem with the larger general economy.
We saw a surge in prices around 2007/08 as collectors were fuelled by easy credit together with the use of Self-Managed Superannuation Funds (SMSF's). It was more economical tax-wise to use money in your SMSF than to pay cash that was taxed at higher rates. However, the rules have now changed and collecting books via a SMSF now has must greater restrictions..
The Global Financial Crisis, together with the change in law regarding alternative investments in SMSF's has seen prices generally falling (although rare titles have still maintained their premium).