Christie's charges a Buyer's premium calculated at 23.205% of the hammer price for each lot with a value up to €110,000. If the hammer price of a lot exceeds €110,000 then the premium for the lot is calculated at 23.205% of the first €110,000 plus 11.9% of any amount in excess of €110,000. Buyer's Premium is calculated on this basis for each lot individually.
See for comparison:
Museum of Finnish Architecture, Alvar Aalto furniture, 1984, page 82-83
Amsterdam, Stedelijk Museum, Metz & Co, de creatieve jaren,
Valencia, I.V.A.M., Metz & Co, los años creativos, 1996