Some interesting facts from Sarah Douglas’s story on the mechanics of art auctions published in The Art Newspaper:

• Collectors who donate a work get a tax deduction on its full market value; buyers get one on the difference between the retail value of a piece and what was paid above it.
• Auctioneers are not obliged to abide by the regulations (and the New York State laws) that govern regular auctions, including following specific bidding increments, so have more sway for drawing out bids.
• Artists who donate receive a tax deduction only on the cost of materials.