That calculation wasn't accurate.
I've checked There was around $3,000 saving (probably not including opportunity costs: efficiency, truck utilisation) for interstate dump. $75/t Levy, should be high enough to discourage it.
'It was a mistake for this government to take so long': Labor backbencherFelicity CaldwellFebruary 14, 2019 — 5.40pm
Laws to stop Queensland from being the nation's rubbish dump have been passed.
The waste levy will come into effect in July, at a cost of $75 per tonne to stem the tide of
New South Wales trucks coming across the border to dump rubbish in Queensland landfills.