One of the highest ransoms ever paid — US $60 million for the two Born brothers in Argentina in 1975 — was negotiated by one of the captives himself: Jorge Born. As a company insider, he knew how much money could be raised, but it still took seven months before his captors were convinced that they had truly squeezed him dry. When it finally arrived, the father felt he had no option but to accede to the memorandum signed by his son and his kidnappers. So negotiators work extremely hard to avoid parallel negotiations and bat away unhelpful interventions from the hostage. It is not surprising that some victims despair.
That is from the new and interesting Kidnap: Inside the Ransom Business, by Anja Shortland.