According to the SMH today, the Tourism and Transport Forum has again called for a more reasonable charge for services to or from the Airport. They quote a paper from the NSW government in 2011 which put the value of Airport Link Company at $276 million. Unfortunately, this price would be increased due to the 70% patronage increase at Green Square and Mascot after the surcharge was removed as one of the last acts of the last state government. That should add around $56 million to the price, for $332 million plus inflation, less a couple of years life left in the asset.
If it can actually be bought at this price, they should absolutely go for it. Even Infrastructure NSW can see the need for lower fares to the Airport, in their "First things first" report. Why they aren't doing so requires a detailed explanation.