Costs to secure the hostages release were 'enormous'
Germany has warned 14 European tourists released from captivity in Mali against trying to sell their story for profit.
Defence Minister Peter Struck said the costs for securing their release had been "enormous" and any fees for photos and stories should be given to the states involved.
Speculation has raged about whether Germany or other states paid a multi-million ransom to secure the hostages' release.
Mali's chief negotiator has told the BBC that Germany paid no ransom for the 14.
Amadou Baba Toure, who is governor of the Gao region of eastern Mali, said the team of mediators had had to win the trust of the kidnappers by praying, eating, drinking and talking together for two days.
He said Germany had refused to pay money to the captors because it would have encouraged kidnapping around the world.
The nine Germans, four Swiss and a Dutchman landed in Germany on a military plane on Wednesday from Mali's capital, Bamako.
February/March: 32 European tourists, trekking through east Algerian desert in seven groups, are
13 May: Algerian troops storm hideout near Tamanrasset, freeing 17 hostages
June: One woman hostage, now being held in neighbouring Mali, dies in captivity
19 August: Release reported of last 14 hostages in Mali
They were among 32 Europeans originally captured in Algeria from February onwards.
The Algerian authorities have blamed an Islamic militant group, the Salafist Group for Preaching and Combat, for the abductions.
However, one of the freed hostages, Dutch national Arjen Hilbers, said the abductors were always vague about their identity, referring to themselves only as "mujahideen".
The German defence minister appeared to hint that much of the cost of the hostages' release had been incurred by the deployment of German troops in both Algeria and Mali.
"The costs are enormous," he told German newspaper Welt am Sonntag.
"With consideration for taxpayers, we should expect that people don't make a profit from their kidnapping but make fees for photos and
stories available to the state."
He also said Germany was planning to increase its elite
Commando Special Forces unit to some 1,000 members from 450 "for difficult tasks such as freeing German citizens".
There has been speculation that Libya, which is currently seeking better ties with the West, may have paid the ransom for the hostages.