That seems very expensive. I would have thought a taxi would be about half that. I live about the same distance from the airport as going to the city and a taxi costs me about $25. Scope Swan Taxis.
The Hilton indicates $50 estimated taxi cost each way. I seem to recall it actually costing me $30-35 each way for a taxi when I was there a couple of years ago, maybe a little more for the one from the hotel to the airport being for a 5:15AM flight out.