F70 and F100 are around $9,000 per/hr AUD and a B737-800 will be anywhere from $10,000 - $12,000 per/hr AUD. This includes crew etc. and may not include any catering.
Where for example the Norfolk Island Government chartering an aircraft each week falls down, is that there are rules regarding selling individual seats on a charter flight. Just ask Tiger Airways about this.
While a charter flight type arrangement might be better suited to this route, because of the rules a RPT carrier needs to be used and have a schedule etc. Which then means the carrier may fly the schedule with less than required loads to either break even or make a profit.
Another question that needs to be asked is, is this route a route which requires a 100 seat plus aircraft for each flight? Going back a number of years now when I had a little involvement with this route, I'd say it isn't. If that is the case then maybe someone like Jetgo may be better suited (not sure of the aircraft performance) to this route?