Princess Diana and Dodi Al Fayed, son of Mohamed Al Fayed, owner of London's Harrods, perished alongside chauffeur Henri Paul when their Mercedes slammed into a pillar in the Pont d'Alma tunnel, in Paris, on August 31, 1997.
The figures for the five-month long coroner's inquest showed costs for the period up to the end of February reached nearly 3 million pounds ($6 mln). The investigation into the car crash that killed the princess has so far cost almost 4 million pounds ($8 mln), Coroner Lord Justice Scott Baker said on Friday.
The inquest to investigate allegations that Diana and Dodi were murdered was first launched in 2004. However, it was stopped mid-way during the investigation, and resumed only in October last year after a break of nearly three years.
Inquest officials said the figures were released in "the interests of openness." The figures do not include the fees paid to the judges. A separate bill for legal services and MI6 has not been made public.
The bulk of the bills are paid by the Ministry of Justice. In addition, tycoon Mohamed al Fayed, has spent around 3 million pounds on the investigation.
The 11-person jury is set to convene on March 31 to hear a summary of the case and to later announce a final verdict on the inquest.
The death of Princess Diana and Dodi saw subsequent mass mourning in Britain, with unparalleled outpouring of grief and shock, as well as a host of conspiracy theories.
Mohamed al Fayed alleged that Diana was pregnant with his son's child, and that the British establishment, not wishing to see her give birth to a "Muslim baby," ordered the princess' murder.
Dr. Robert Chapman, who was in charge of Diana's post-mortem, however rejected this theory saying that the princess' womb and ovaries had shown no signs of pregnancy.