QCAT because seller is in QLD and they hear matters relating to The Australian Competition and Consumer Act (which all states adopt incl NSW (so it is a NSW law anyway)), Furthermore state ACTs mirror each other ie each state has their "goods act" which essentially only differs in title ie (QLD) Sale of Goods Act 1896 , (NSW) Sale of Goods Act 1923, (VIC) Goods Act 1958

Nobody, not even eBay ,can limit someones rights and put jurisdictional restrictions to prevent them from exercising those rights.