" cost is effectively more to do with the need to replace parts, than actual hours accumulated."
I have to be a bit careful here. Most major components are repalced because of time. The airframe itself just accumluates hours. Each major component has a lifetime after which it is either destroyed as in Rotor Blades or rebuilt as in Engine, Transmission etc. If problems occur between times you will also have to consider added expense. Non time life items are usually repair as needed, seats, interior etc.
There is a chart out with operating costs for most helicopters but its a guide or reference rather than etched in stone.
Im also hoping others will get in on this and bail me out a bit as Im just a Pilot not a Maintenance type.
Your initial purchase of a Helicopter should be determined by what you plan on using it for. If you are doing work in the bush, slingloads etc, the aircraft does not have to have all the bells and whistles. wheras if you are using the same type aircraft for VIP transport etc. in comes the leather interior, Bose Headsets and other toys. Many different uses for a helicopter and therefore the inital investment for the same basic helicopter can go from very low to very high.