World's most expensive feather

A single feather of the now extinct New Zealand huia bird has set a world record after being sold for NZD$46,521.50 ($28,417, £22,409) at an auction.  The feather, initially expected to fetch up to $3,000, broke the previous record which was for a feather of the same species by 450%, the Webb's Auction House said.

The huia bird was sacred to the Māori people. Their feathers were often worn as headpieces by chiefs and their families and also gifted or traded. Its last confirmed sighting was in 1907, but unconfirmed sightings were reported for twenty to thirty years after that, according to the Museum of New Zealand.

The feather is registered as a taonga tūturu under a system to protect Maori made objects. Only collectors who had license in the system were allowed to purchase it, and it can not leave the country without permission from the Ministry of Culture and Heritage.

In the past, the huia feathers were a status mark to Māori people. Already a rare bird before the arrival of Europeans, the species became a target for collectors and fashion merchants after it gained popularity among those who came to New Zealand, which led to its extinction, according to the Museum of New Zealand. 

Some additional details at the BBC.  The Museum of New Zealand adds this info:

The huia was not a strong flier – like the kōkako, it was more of a flighty bounder as it worked its way through the layers of the forest.  These forest dwelling species have all been very sensitive to the effects that the arrival of humans and other mammals has brought to their environment. 

The decline in numbers would have started from the first Māori settlers, with their hunting, and predation by the animals they brought – kiore, the Polynesian rat, and kurī, the dog. Europeans brought new hunting animals, and also stripped the land [North Island] of large areas of forest.