While I agree have yet to see any proof this law is being enforced!I’d have to defer to my legal council (SYD+1) for the actual legislation but the ACCC website is pretty clear.
Card surcharges
If a business charges a payment surcharge, it must be able to prove the costs it's based on. If there's no way to pay without a surcharge, the surcharge must be included in the displayed price.www.accc.gov.au
Basically, if they don’t take cash and the only way to pay includes a surcharge then they have to build that into the advertised price. Not add it later.