I paste from your link:
"The Government of Australia requested a possible sale of the AEGIS Combat System and select combat system and communication components consisting of 3 AN/SPQ-9B Horizon Search Radars, 3 Cooperative Engagement Capability Systems, 3 Naval Fire Control Systems, 3 Multi-Functional Information Distribution Systems, AN/SLQ-25A Nixie Countermeasure Suite, MK160 Gun Computer System, AIMS MK XII Identification Friend or Foe (IFF) for the Air Warfare Destroyer platform, communication and information distribution systems, U.S. Government and contractor engineering and logistics personnel services, personnel training and training equipment, support and test equipment, spare and repair parts, publications and technical documentation, and other related elements of logistics support. The estimated cost is $450 million. "
That price is not only for Aegis combat system (radars and hardware and software for the Spy), but includes many things of the Aegis Management combat system and other things
That is because i bold one thing and italic the other in above text.
So actually the Spy and its Aegis is less than 150 mill dollar.
Edit: above it is mentioned "Aegis combat system" but let me have doubts whether it is including the Spy there or just other hardware and software related to it. It doesn´t sound bad like 150 mill dollar per Aegis combat system (incl. Spy) as you say.