Is the Presidential race a waste of money?

[WonderFromDownUnder]

Living in another democratic country (Australia) I can't understand why the American system seems to waste millions of dollars picking a President. After an election is decided here, both the incumbent party and the Opposition hold meetings to decide which elected officials (Ministers) run which portfolios, including Leader of the Opposition and Prime Minister (= President). I don't understand why the position of President of America is decided by a seperate and very expensive ballot when the American people have already elected the Party they prefer.