Not sure about the cost to install but wanted to comment on the cost to run. The town house we live in (4x2.5 and 199sq metres living space) has ducted reverse cycle air conditioning. We've been here a year now and our bill has never been over $600 per quarter with frequent use of both the heating and cooling.
By comparison to running the split system airconditioners in FNQ I would say that the ducted system is a lot more energy efficient and therefore cheaper to run.
Agree. We have a massive 6 bedroom house and in winter when it's on it's only 100/ month which is very good considering the size of the unit. Think one of those porta loos in size. We don't run it in summer as we live up high and don't really need it but winter is very cold. We have double glazing so I run it all night on cheap power and don't turn it back on again till after lunch.