The actual cost of the new carriage is unknown. It has largely been financed by its builder, Jim Frecklington of Sydney, assisted by corporate, public and visitor donations.
What is known is that the Australian Government allocated A$250,000 in May 2007 with the promise of a further A$100,000 to help with freighting the carriage (which weighs just under three tons) to London. The carriage has taken over four years to build.
The Telegraph estimate of £620,000 is equivalent to A$1.4m, US$883,000, Euro€686,000.
Mt Frecklington also built the other modern royal carriage, the Australian State Coach, in the mid 1980s. I saw this coach up close when it was on display before being shipped to London and apart from the craftmanship and exquisite detail, the overriding impression was the sheer size. These things are huge.