Here in the good old Mother country we have to agree depreciation of business assets with Her Majesty's Revenue & Customs. One way of depreciating an R44 is one-thirteenth of its cost per annum for 12 years. Or you can choose to depreciate at a set figure per hour - which I believe for a standard R44 is around £60 or Aus$ 145
The basis of all this, of course, is the 2200 lifetime or 12 years, whichever comes first.
These costs are in addition to your FOC & DOC.
Not certain what you mean by "2000" hr rebuild. For DOC you should allow for at least a 50hr and 100hr - and some places like to change the oil every 25hrs. (Some R44s also use a litre of oil evey 3hrs) With a 2 yr warranty, new machines are initially cheaper to run - but do make some sort of allowance for "exceptionals" once the 2 years are up.