It can be. Depends on how you use it. My first bill, after I built my house, was around $800! We did use it a lot. After that, we would only put it in late afternoon to warm up the house at night, close all the doors and block the vents in rooms that weren't being used. We used door snakes to help prevent heat from escaping. We noticed a huge drop on the next bill.

If you run it on say 18 degrees to take the chill of, it's way more efficient. You can also program it to come on and off at certain times, particularly when you're not home or outside. Ours is programmed to kick in at 6am and turn off at 9pm. Some can be zoned living separate to bedrooms also. Make sure you have draught stoppers and windows and doors are tightly sealed. Ours is quite efficient.

I wouldn't buy a ducted unit unless I had a big house. They are expensive to run and cost a lot to replace. If you have an average size home split systems are more efficient.

We have gas ducted heating and gas stove top.
Our summer quarter bill (the heater hasn't run at all) was $85- most of which is supply charge, our winter quarter (heater set to 20 during the day and 16 overnight) was $1045. We haven't had electric to compare, but we are happy to pay to be comfy. Note we're in Canberra, it gets really cold.