Why do kidney prices vary so much?

An Aussie physician suggests paying $47,000/kidney. In an earlier post, we reported that Iran pays kidney donors less than $1,200. So why is the proposed price so high in Australia?

Australia has one of the lowest rates of organ donation in the developed world, about 10 donors per 1 million people, according to a federal health task force. ... In comparison, Germany has 15 donors per 1 million people, the Netherlands has 25, the United States 27, and Spain 35...

"We've tried everything to drum up support for organ donation and the rates have not risen in 10 years," Carney was quoted as saying in Fairfax newspapers. "People just don't seem to be willing to give their organs away for free. ... Let's pay people some money for a new car or a house deposit and those waiting lists will be halved within about five years."