Laetitia Guilbaud's portrait of British Prince William's sister-in-law failed to sell at auction last year, but a rear-view, painting of Middleton fetched $2,700, The Daily Telegraph reported.
"Obviously, first time round Laetitia didn't fully realize that Pippa's best asset -- and what has shaped her character in the public's mind -- was her rear," said Marcus Macleod, of Braewell Galleries, in Edinburgh, Scotland.
German fashion designer Karl Lagerfeld said last month Middleton should "only show her back" since she "struggles" with her appearance.
Couple mistakenly served bag of cash at McDonald's drive-thru
Kate Middleton recycles dress at movie premiere