The Duke and Duchess of Cambridge were awarded the large payout £92,000 after long-lens images of Kate sunbathing on a terrace were published by France’s Closer magazine in September 2012.
The pictures show Kate only wearing skimpy bikini bottoms, with William applying sunscreen on her skin.
The editor of Closer magazine, Laurence Piea, 51, and Ernest Mauria, 71, the director of the Mondadori group which publishes it, were fined £42,000 each for violating the privacy law.
But barristers say the sum was excessively too much because compensations of privacy complaint are usually in the range of £100.
The French lawyers say the couple did not deserve the payout for topless photos of Kate by using Meghan Markle’s old sexy shoots as a proof, saying modern titled women have used steamy body shots to promote themselves in the past.
The proving video entitled "Grilling Never Looked So Hot With Meghan Markle", shot for Men’s Health magazine in 2013, shows Meghan seductively stripping off her shirt for the camera while grilling hamburgers.
The appeal will start in the Versailles Appeal Court tomorrow. Other evidence for it may include images of Meghan exposing her breasts for the camera on a beach, taken before joining the Royal Family.
Even though Kensington Palace sources insist the photos of Kate were tampered or stolen, they are still widely circulated online.
Closer's lawyer Paul-Albert Iweins says the fines were "exaggerated for a simple privacy matter" while French fines are often less than £100.
Counsel for the convicted point out that younger Royals are increasingly like celebrities, so they treated them somehow like actors and sports stars.
"They are happy with sexy photos of themselves when they are in control, but then claim huge amounts of money when they’re unauthorised," said one legal source involved in the case.
"There’s ridiculous hypocrisy involved, and the outrageous compensation figure reflects this," said the lawyer.
Photographers, who still deny guilty, were also fined the equivalent of up to £8,500 each, after William presented statements attacking the paparazzi.
He and Kate wanted £1.4 million, but following the Nanterre payout, a Kensington Palace spokesman said they considered the case closed.
The Duke and Duchess of Sussex hav ...
A federal judge dismissed Stormy D ...