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Hi Krecik. The simple answer to 'are there any books discussing quantities and rarities of designs' is 'No'. I don't think I have ever seen two Saint-Louis mushrooms that were the same - they were in effect one-offs, not some form of limited edition. Regarding wildly varying prices, that sometimes appears to be the case, but it is important to distinguish between the asking price you might see, and what an item might have been sold for...and if it has not yet sold, there may be a message there about the asking price!
Alan