Exactly.
Let's say that Miles St Stickleburn buys a rare collectable stamp, the Kaiser Wilhelm II invert (1905). It's sold on eBay.de at a price that is unbelievably low due to the seller having misspelled everything important, and having listed in the wrong category; the total including postage is about $950, and Mr St Stickleburn is outraged to be charged 10% GST upon winning the bid. However, as an avid philatelist, it's pay up or lose out, and he doesn't want to lose this stamp. He pays up. (It's a great price, too.)
Years later, after Miles dies as a result of being attacked by an aggressive echidna (infected wound), his estate passes to his younger sister Pasteurilia St Stickleburn. She despises stamp collecting, and puts up the whole collection on eBay. It's snapped up by Joe Blaugum who lives in Far North Queensland but who doesn't begrudge the 8-hour drive to Ms St Stickeburn's house to pick up the stamp collection. He pays no GST, because Pasteurilla isn't running a stamp business. For that matter, neither was her brother, Miles; he was just a rich collector.
Joe Blaugum's sister's eldest boy Bazza is abducted in China, and the kidnappers demand a huge ransom. Joe's sister suffers a heart attack in the crisis and it's up to Joe to save his nephew. Joe has to realise cash fast, so he is obliged to sell the rare stamp collection quickly. He doesn't trust eBay any longer (after a horrible experience with selling an iPhone), and is confused by the whole GST thing on second-hand items, so he takes the stamps to a philatelic shop and negotiates the best price he can, in a hurry so that he can meet the deadline and pay the kidnappers.
(It turns out that Bazza was never abducted; it was all a huge scam. Bazza appears a week later after doing some spelunking in the Cuevas del Drach in Spain. Too late for Joe; the money's gone, and he can't get back those stamps, either.)
Now, so far the only one to have paid GST was Miles, because he bought the stamp on eBay for less than $1000, from an overseas seller. eBay collected the GST and remitted it to the ATO. Miles's sister didn't have to pay GST, and there wasn't any inheritance tax. Joe didn't have to pay GST because he bought from a private individual, not a GST-registered business. This remains true even though Pasteurillia sold the stamps on eBay.
The shop of course would have calculated and reported one eleventh of the purchase price of the stamps into the GST credits column. Now the philatelic shop puts up the stamps for sale, and a man called Buick Tussel buys the Kaiser Wilhelm stamp. The price he pays includes GST, and the shop of course would be paying GST - or rather, off-setting the GST payable with the GST credits, and if the shop's made a total credit over the last period, of course it would have a GST liability to pay. (Simplifying it a bit.)
Now, up jumps Buick Tussel, and he could shout out that his purchase price paid for the stamp shouldn't have been GST-inclusive because GST has already been paid on it by Miles, who imported it. That would be faulty logic.
The moral of this story is ... don't go spelunking.
(There would have been a more convoluted history here if Miles's sister had sold the stamp to an overseas buyer, who then listed it on an international website where it was sold to another Australian buyer who then paid an extra 10%... and that buyer then bequeathed it to a professor friend of his in Oxford, and the professor kept it only for a short time as he was murdered by a rare South American poison in his sherry, and the stamp was stolen by the murderer and then put up for sale on eBay, where it was purchased by an alpaca farmer in Gippsland (so another lot of GST collected), and so on... but the chances of that happening are so small that this isn't a story idea with which I'm running. Besides, I still have a promise to fulfil viz-à-viz the Danish mystery, so The Curious Travels of the Red Inverse Stamp: a tale of blood and philately, is not a story you'll be reading any time soon.)
