How does the appraiser determine or estimate what that amount should be?

By taking the difference between the ordinary and the extraordinary. All things being equal, if the difference at auction between the plain cookie jar and the Warhol cookie jar is a factor of 15, then one would use 15x (the premium) the ordinary value to yield the donation value (FMV). ….Actually, we would have to use the retail price of the ordinary jar (not the auction price (FMV)) and compare it to the Warhol jar, assuming that the Warhol jar went to a retail buyer, which it probably would. Generally, those types of auctions (for Jackie-O, Warhol, etc., stuff) go directly to the retail buyers.  more

By taking the difference between the ordinary and the extraordinary. All things being equal, if the difference at auction between the plain cookie jar and the Warhol cookie jar is a factor of 15, then one would use 15x (the premium) the ordinary value to yield the donation value (FMV). .Actually, we would have to use the retail price of the ordinary jar (not the auction price (FMV)) and compare it to the Warhol jar, assuming that the Warhol jar went to a retail buyer, which it probably would. Generally, those types of auctions (for Jackie-O, Warhol, etc., stuff) go directly to the retail buyers.