A Canadian work of art that was traded for a grilled cheese sandwich 50 years ago has sold at auction for an "astounding" C$350,000 (US$272,000).

Folk artist Maud Lewis' painting Black Truck was sold for ten times its appraised worth, reaching a new record for a painter whose fame has risen in recent years.

Ethan Miller, head of the Ontario auction house stated that “In a time of great turmoil and change the art world lived vicariously through Maud Lewis, her story, and her art."

Prior to the weekend auction, the highest price ever paid for a Lewis piece was C$67,250.

Lewis spent much of her life in poverty, and her production as a painter dwindled in her latter years as the symptoms of rheumatoid arthritis took control of her body.

While she and her husband sold paintings to visitors passing through Nova Scotia, her unique and cheerful art did not achieve international recognition until decades after her death.

Her difficulties and triumphs were recounted in the 2016 film Maudie, which brought Lewis' work to a wider audience. The purchaser of Black Truck boosted their initial offer increment by C$10,000 after seeing the film the night before the auction, according to the auction company.

Irene Demas, a young cook who obtained the work of art in return for a grilled cheese sandwich, told The Guardian in an email that she was in "disbelief" at the occasion.

She and her husband, Tony, had made an arrangement with artist John Kinnear in which they would be able to choose from a variety of paintings by Kinnear and, under certain circumstances, works by his friends in return for grilled cheese sandwiches.

“Mind you, it wasn’t just an ordinary grilled cheese. It was a great sandwich, with a five-year-old cheddar and beautiful bread,” she told The Guardian in early May.

Kinnear brought in a series by the Maritime artist, whose particular style captured his attention and whose challenges tugged at his heartstrings, one morning in 1973. Among those paintings was Black Truck, which has been hanging at Demas' home for the past five decades.

Lewis praised Kinnear in a series of emails for his compassion and generosity in providing her with the paints and prepared boards. The three handwritten letters, which were also on the market, sold for C$70,000, considerably above their $5,000 estimate.