The British taxpayer was hit with a £50,000 bill for five helicopter flights taken by Prince William for occasions such as a stag party and a visit to his girlfriend's family home.
The flights drew criticism as an alleged abuse of the Prince's RAF training, which ended in April.
Ministry of Defence figures, released after a freedom of information request by The Guardian, have now shown exactly how much they cost.
The Chinook flight William took to attend a stag do on the Isle of Wight was worth £8,716.
The prince also used the military aircraft to fly over Highgrove, the Gloucestershire home of his father the Prince of Wales, and over Sandringham, the Queen's residence in Norfolk.
A further Chinook trip took the royal to Hexham, Northumberland, where he joined a wedding party.
A MoD spokesman said tonight: "All flights undertaken by Flying Officer Wales were a legitimate part of his RAF training.
"In retrospect, there was a degree of naivety in the planning of the training sorties that either allowed Flying Officer Wales to attend private functions or land and take off (20 seconds later) from a privately owned field.
"This should not detract from what was an extremely successful and valuable attachment for Flying Officer Wales.
"He displayed natural flying ability and was able to gain an invaluable insight into the roles and capabilities of a modern air force."
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