Complex sentence: The six "Collins" class submarines are the most expensive items of equipment in the Australian Defence Force, with the estimated annual cost of operating and maintaining the class estimated at AU $100 million in 2000, and at AU $322 million in 2008.
Split into simpler sentences: The six "Collins" class submarines are the most expensive items in the Australian Defence Force inventory. The annual cost of operating and maintaining the class was estimated at AU $100 million in 2000, and at AU $322 million in 2008.