“Values can be inflated when auction houses offer competitive guarantees to secure major consignments. These guarantee can then be transferred to a third party, who will either buy a work at a sale, or be rewarded for their unsuccessful bidding. More recently, some third-party guarantors — called “irrevocable bidders” at Sotheby’s — have also been paid fees if they are the purchaser. These confidential arrangements, denoted by symbols in the catalog, can have the effect of deterring bidding in the salesroom.”