The Big Hoot art trail has seen 89 owls, 5ft 5ins (165cm) tall, dotted around Birmingham for 10 weeks.
The statues were designed by artists, celebrities, community groups and schools.
Money raised from the sale at Thinktank, Birmingham's science museum, is to go to the city's children's hospital for a new rare diseases unit.
A statue called Re-Tail by internationally-recognised graffiti artist Temper attracted the highest amount, £18,000, the hospital said.
Ozzy's Owl, which was co-created by Black Sabbath frontman Ozzy Osbourne and another artist, fetched £12,500.
Osbourne gave a video message saying how much he had enjoyed designing it and having the statue put in Birmingham.
Dr Hoot, based on Dr Who's Tardis, fetched £10,500.
Paul Larkin, a market trader in Birmingham, was part of a group which paid £8,500 for an owl called Unity Within Diversity.
He said "traders from Birmingham rag market all pitched in together" to buy it "for such a good cause" - the hospital - and the owl would go in the market entrance.
Asked if he had a big shed at home, Mr Larkin said: "No. This is better off in the market... It's going to stay in Birmingham. The people of Birmingham can enjoy it."
Following the 10 weeks, the decorated owls, individually designed by professional and amateur artists, went on public display again at Millennium Point on Saturday and Sunday before the auction on Thursday evening.
An app to accompany the project was downloaded over 13,000 times and people have scanned the owls with phones more than 323,000 times, organisers have said.
Speaking at the auction, hospital director of fundraising Louise McCathie said: "It's just been outstanding. We knew it was taking off, we knew it was big,
An auction of giant decorated owl statues, which were part of a city-wide art exhibition, has raised £508,000.