Eugenie is marrying her long-term boyfriend Jack Brooksbank in a lavish weekend-long affair early next month.
The wedding is reported to be costing around £2 million, but most will be footed by the taxpayer as security costs.
However, the rest will be paid for by the Yorks and the Brooksbanks. With such an expensive wedding bill to pay, how much is Sarah actually worth?
According to TheRichest.com, Sarah is worth around $ 1 million, which is approximately £751,000.
Sarah was once the official Duchess of York, part of one of the richest families in the world.
But her marriage to Prince Andrew broke down in the late ‘90s, with the couple divorcing in 1996.
It is claimed that Fergie didn’t receive a huge payout, and knew she had to work hard to keep up her lifestyle.
Since the divorce the 58-year-old has kept her name firmly in the public eye, working as a writer, public speaker, charity patron, brand ambassador and television personality.
She has worked with countless brands over the years, endorsing products and speaking at events, all helping to build her bank balance.
She has held contracts with British fine china and porcelain company, Wedgwood and cosmetics giant, Avon.
Perhaps one of the duchess’ most lucrative deals, she held a decade-long endorsement with Weight Watchers, no doubt contributing to her $ 1 million net worth.
Sarah will be footing some of the bill for Eugenie and Jack’s lavish wedding
Fergie has also dabbled in writing, having written various books including two autobiographies.
She has also hosted radio shows and the 2009 ITV reality show, The Duchess on the Estate.
The controversial TV show saw the Duchess journey to a working-class estate in Manchester for a fly-on-the-wall documentary. This was followed by another called The Duchess in Hull.
Fergie still currently lives with her ex-husband in the Royal Lodge in Windsor.
The two also own a £13 million chalet together in Verbier, Switzerland.
It is believed she also rents her own apartment in the expensive Eaton Square in London.
Before joining the Royal Family Fergie had a string of jobs, including working at a PR firm.
Her story is very similar to that of Kate Middleton, who worked before marrying Prince William and banked a huge pre-wedding net worth.
Sarah Ferguson: Five facts about the Duchess of York
Sarah is the second daughter of Major Ronald Ferguson and Susan Mary Wright.
Her parents divorced in 1974, with her mother going on to marry polo player Héctor Barrantes in 1975 and moving to Argentina. Sarah stayed in the UK with her father, who remarried in 1976 and went on to have three more children.
Sarah married Prince Andrew on 23 July 1986 at Westminster Abbey in London.
She wore an ivory-silk wedding gown designed by Lindka Cierarch which had a 17 foot train and 20 foot veil. As is tradition, Sarah wore a diamond tiara, and her wedding band was crafted from Welsh gold.
The couple spent their honeymoon abroad the real yacht Britannia off the coast of the Azores Islands.
Sarah and Andrew divorced in 1996 after separating in 1992.
However the couple remain on good terms, even living together in the Royal Lodge from 2008 until Sarah moved to a ski chalet in Switzerland they bought together in 2015.
Sarah has written children’s books for many years, her first being a series about Budgie The Helicopter in the early 90s.
She has also been the US spokeswoman for WeightWatchers after famously battling her weight over the years.
On top of commercial endeavours, the Duchess devotes plenty of time to charity, including Children in Crisis, which she founded in 1993.
Fergie, as she is known to friends, uses both Twitter and Instagram.
She has over 200,000 followers across the platforms, and shares many insights in to her life.
Most of the Royal Family are not on social media, but are represented by Kensington Palace, Buckingham Palace, or Clarence House.
Sarah’s daughters, Beatrice and Eugenie, are the exception, with both joining their mother on social media.