She was talking about the selling of newspapers and magazines, but the same was equally true of almost anything she touched. Diana as commercial property was an advertising manager's dream.
The clothes she wore, the water she drank, the charities she supported; like Midas, the touch of the princess performed miracles in sales and publicity as the public continued to be fascinated by the upper-class girl who had married into a fairytale that turned sour.
Not that it mattered. Recent pictures of the princess with her friend Dodi Fayed in August were thought to have sold at least 750,000 extra newspapers, according to latest figures. At the time, Stuart Higgins, editor of The Sun, said that no one excited the interested of his readers so much. "There is an absolute fascination with her that never wanes from our readers' point of view." His paper alone sold an extra 175,000 copies the day the fuzzy snaps purporting to show Diana embracing Dodi were published. The Sunday Mirror, the first paper to print the pictures, saw more than quarter of a million sales put on.
But the selling power of the most photographed woman in the world was not only true of the newspapers and the paparazzi whom she blamed for hounding her. Magazines with a picture of Diana on the front could see a circulation leap of as much as 30 to 40 per cent, according to media commentator Michael Leapman. "Her effect on circulation was quite phenomenal," he said. "That is why her picture appeared on so many covers. There hasn't really been anything like that, except for maybe Liz Taylor in the old days or Princess Grace of Monaco, and there wasn't the same level of hysteria."
Leonie Jameson, a documentary maker who has worked on the acclaimed Secret History series, and who has been researching the history of the relationship between the media and the monarchy for Channel 4, thinks our fascination with Diana was partly due to the princess's ability to transform herself from Shy Di to glamorous fashion icon to caring charity worker. "I think it was Stuart Higgins who described her as a cross between Cindy Crawford and Mother Teresa of Calcutta," she said, highlighting interest in a photogenic young woman would have waned otherwise. "There is an anecdote about a woman's magazine putting her on the cover for 36 weeks in a row. When they took her off, sales went down."
The books industry also benefited from the princess. Robert Lacey, who wrote Princess, one of the first books on Diana in 1982, recalls coming back from overseas in the 1980s to discover a phenomenon called Diana Spencer. "She wasn't a royal phenomenon but something completely new," he recalls. "I remember going past the window of a jeans shop and seeing a photocopied cheque of Lady Diana Spencer's in the window because she had bought something there. From the beginning, there was this magic that surrounded her."
Lacey's book proved a runaway success, staying for 27 weeks on the New York best-sellers list. But the real explosion came a decade later. Andrew Morton's book, Diana Her True Story, published in 1992, revealed details such as the princess's struggle with bulimia and the hollow nature of her marriage. By the end of the year, his publishers, Michael O'Mara Books, claimed to have sold three million copies in 23 languages, including Korean and Icelandic, and it was estimated that Morton would have made pounds 3 million from the book. News International also paid pounds 240,000 for serialisation rights to his account in the Sunday Times and The Sun, for which the author negotiated a deal securing him 85 per cent. Even Anna Pasternak's book, Princess in Love, about James Hewitt and Diana, sold 75,000 copies in the first 24 hours.
Her success was not even confined to pictures of her or words written about her. When Diana started driving an Audi Cabriolet 2.6E in 1994, the German car giant Volkswagen saw sales rocket from 568 to 989 in a year, adding pounds 10.2m to Audi UK's annual revenues. British fashion designers for years enjoyed her loyal custom. In public, she would only wear British.
Harvey Nichols, San Lorenzo, Evian water and Reebok trainers also basked in the glow of her patronage. A survey by Majesty magazine three years ago calculated, by measuring the column-inches of mentions in tabloids, that the Princess generated pounds 14.5m-worth of free publicity for products she bought.
The San Lorenzo restaurant, a favourite lunching spot of the Princess, enjoyed pounds 25,000 of free advertising, the magazine calculated. Harrods got pounds 21,000, the Chelsea Harbour Club pounds 73,000, Chanel pounds 12,000 and Evian water pounds 59,000. Disney World, where she took sons William and Harry, garnered more than pounds 129,000 worth, and Marks and Spencer pounds 87,000. Her favourite charities benefited, too, the Red Cross getting pounds 40,000-worth and Relate pounds 44,000.
Diana herself strove to use the phenomenal attention to her own ends to promote the charities and causes she was interested in. The recent auction of her dresses in New York raised pounds 3.5m for charity - Richard Martin, curator of the Costume Institute at the Metropolitan Museum of Modern Art, called them "holy relics of a great Cinderella story of our time" - and it was rumoured that the asking price to sit next to her at charity dinners was as high as pounds 100,000.
"As I have all this media interest, let's not just sit in this country and be battered by it," she told Martin Bashir in the Panorama interview. "When I go abroad, we've got 60 to 90 photographers, just from this country, coming with me, so let's use it in a productive way, to help this country."
With Diana's life so cruelly cut short, is there anyone who could replace her in these iconic terms? "Not really," says Michael Leapman. "There is nobody else. Maybe when Prince William leaves school and people write about his girlfriends, he could become a male version of his mother. But there is no other figure like her"n