According to media reports, the cost to hire a private hostage negotiator to negotiate a ransom payment with Somali kidnappers is roughly $2,000 per day. The fee does not include the negotiated ransom payment.
The fee was disclosed in an article about two individuals who were held hostage in Somali in 2008. The hostage takers originally demanded $3 Million in ransom to release the two individuals. After discussions with the private negotiator, the eventual ransom payment was $600,000.
Source: Chris Purdy, “Canadian kidnap victim reveals details of ordeal,” Province, August 19, 2013.