A copy of James Audubon's famous Birds Of America sold at Sotheby's for over £7 million. The new owner, Michael Tollemache, a London dealer, could be said to actually have more money than sense as he described the work as "priceless". It's not clear whether that statement was before or after handing over the cash of the price.
Some interesting quotes from the Wiki page on Audubon;
Colorists applied each color in assembly-line fashion (over fifty were hired for the work). The original edition was engraved in aquatint by Robert Havell, Jr. ... Known as the Double Elephant folio after its double elephant paper size, it is often regarded as the greatest picture book ever produced and the finest aquatint work.I suspect the British Library and fellow Crown libraries have copies now.
He followed Birds of America with a sequel Ornithological Biographies. This was a collection of life histories of each species written with Scottish ornithologist William MacGillivray. The two books were printed separately to avoid a British law requiring copies of all publications with text to be deposited in Crown libraries, a huge financial burden for the self-published Audubon.
Apparently the cost of printing the Birds of America was US $115,640 (over US $2 million today, or £1.3 million). When the project stuttered during an enforced absence, he told the wary few (of his otherwise loyal) subscribers: "'The Birds of America' will then raise in value as much as they are now depreciated by certain fools and envious persons."
In the same Sotheby's sale a 1623 First Folio Shakespeare cost a buyer £1,497,250.
