Don't just look at how many kilometers difference it is
It is well over 1 hour 15 minutes with no traffic issues to KSA and that is outside morning and afternoon peaks where the time easily doubles
Plus avoiding KSA is an added bonus
Factor in parking costs and travel time etc and the likes of JetGo with the right size aircraft should be able to make a go of it
That said, I would have thought that the Gold Coast may have been a better choice over Brisbane why?
Melbourne - Albion Park - Gold Coast - Rockhampton - Townsville - (add in Cairns) and return daily and that opens up endless possibilities of getting bums on seats
No surprise that Melbourne - Port Maq failed
Port Macquarie is more of a Sydney getaway for the weekend, mostly by car and a stop off for the Grey Nomads, I wouldn't think that many from Melbourne would consider Port Maq high up on the list for a holiday, so they would have had to rely mainly on business travelers and locals going to Melbourne
A lot of the Port Macquarie air transport is getting passengers, mostly retirees to Sydney and onto international flights