Meghan Markle will have to pay £67,000 ($130,500) in legal costs after losing the first round of a court battle with Associated Newspapers Limited.
Markle is suing the company, which publishes the Mail and MailOnline, over a February 2019 article which published parts of a letter she sent her father, according to the Daily Mail.
A written submission from July 22 showed that Markle agreed to pay the publisher's costs for the strike-out hearing.
The bill was revealed as the court heard Markle believed that naming the friends who told People magazine about her letter to her father was an "unacceptable price to pay" for pursuing a claim against Associated Newspapers.
The Duchess applied for an order to keep the women's identities secret.
Markle's legal team said in court that: "To disclose their identities to the public at this stage is an unacceptable price to pay for the right to pursue her claim for invasion of privacy."
But in an embarrassing gaffe during the application, Markle's lawyer Justin Rushbrooke accidentally revealed the last name of one of the five friends she is seeking to keep anonymous.
Judge Justice Warby, expected to make a ruling in August, directed that the woman's name was not to be reported.
The women were named in a People Magazine article in 2019 and in legal papers submitted by Markle to the court earlier this month.
Antony White, QC for Associated Newspapers, told the court that Britain's principle of open justice meant the friends should be named.
"There is no proper evidential basis [for the application]. There is no evidence at all from four of the five friends and the evidence from the fifth [Friend B] has been shown to be unsatisfactory," he said.
Markle insists that she didn't know her friends had spoken to the magazine until after the article emerged, with all five of the women facing the prospect of going to the High Court in London next year to testify in the privacy trial.
Neither Markle nor Prince Harry were at the hearing today.