I took up the challenge. On a random date, Tuesday 2 March 2021 - deliberately chosen because I guessed Monday would cost more and to ensure that one couldn't say that the booking was close to today's date when it's normal for airlines to bump up fares - the single (one way) fare was A$445.40. Monday was a heartstopping one way fare ex SYD of $698.40, while the cheapest was We/Th with each showing $406.90.
..
Rex really knows how to play Monopoly. Once or twice recently QFd has cancelled its new flights to GFF or OAG, presumably due to lack of demand. These were previously Rex monopoly NSW intrastate routes.
Although I know another carrier, who on a particular monopoly route ex-SYD that is 15% less in distance than BHQ on a similar sized aircraft, where there even fewwer surface transport alternatives (i.e. functionally none), is not charging less than $546 one way over the next two months, and has some flights as expensive as $891 one way.