The Chinese artist Ai Weiwei has sold a ton of the porcelain sunflower seeds he displayed at the Tate Modern for $782,000 (£480,000), a record sum for his work which should help to pay off his tax bill if an appeal against the Chinese taxman does not go his way.

The sackful of handpainted seeds, sold at an auction at Sotheby's in New York, is one of an edition of 10 and is accompanied by a certificate signed by the artist. The artwork was originally displayed in the Turbine Hall at the London gallery but had to be removed because of health concerns over particles of ceramic dust.

The sale comes days after a Beijing court accepted the artist's legal action against a 15m yuan (£1.5m) tax evasion penalty that the government levied against the company that markets his work.

A controversial figure in China, Ai, who collaborated with the Swiss architects Jacques Herzog and Pierre de Meuron on the design of the Bird's Nest Stadium for the Beijing Olympics, was arrested in March last year and held for almost three months before being released without charges. His activism has long irritated the authorities but the artist is a cultural blue-blood in the country, the son of revered poet and Communist Party member Ai Qing and his wife, Gao Ying.

After he was freed, authorities billed him for taxes they said were owed by Beijing Fake Cultural Development, a company controlled by his wife. He said the penalty was "a joke" intended to disguise the fact that his detention was politically motivated. His supporters have donated huge sums to help him pay an £860,000 guarantee needed to challenge the charge.

The artist has said he plans to make every aspect of his appeal public, to allow people to judge for themselves whether he was right or wrong. "Every detail will be posted on the internet and it will be a part of history," he said.