No point buying ASEs from anywhere but the USA or a dealer in Australia with competitive premiums
You can buy monster boxes by the pallet from APMEX if you wanted. There is no GST as it is investment grade and all in, from what I've seen, it is marginally cheaper to directly import from US if you buy bulk.
Either way, there is no reason to buy from ebay. It is a chore sifting through what's there anyway. Most of it is ludicrously overpriced or dodgy af. The fact that people are buying 1938 crowns for $80 tells you there is a sucker born every minute. Caveat emptor.
XRF is helpful. I've noticed some dealers will make a very fine nick in the rim of a bullion item and scan that. Chinese electroplate PMs on the base metals quite thinly in most cases and this ruse would be defeated by that technique.
Regardless, much much better to buy here than ebay or gumtree. You are most likely not trading with a crackhead trying to pay for their next fix, almost always get a better deal and you can quickly determine safe trading partners.
It's not safe at flea markets either. I remember one dealer with a Foy bag for sale in regional Queensland for $120. On closer inspection, the lettering was clearly in dot matrix, the colour of the bag wrong, even the wrinkles were fake, what looked like printed on wrinkles!. The most damning thing was the curvature of the flap, nothing like the genuine article. It clearly was a modern bag. When I pointed this out, the guy asked me what I would like to pay for it. So dodgy!!! Someone with integrity would take it off the market right away.
Imagine repeatedly selling fake 1938s here...you'd be run out of town. I have to say I did buy some 1937s here years ago and the way they were packaged didn't sit that well with me and some don't weigh that well.
On the other hand, I bought a bunch of sovs a long time ago, with some crowns and the stacker I was dealing with had weighed all the crowns and determined a small number were duds, told me and threw them in for free.
Best to go for the less faked items. I don't buy crowns anymore for this reason and the premium for basically a bullion item in the case of the 1937. First 1938 I bought a decade ago had a massive gouge out of the rim which was only apparent when you took the coin out of its protective holder. This was from a note and coin shop no less. Dealer had graded it VF when even a lay person can see the giant dent in the rim makes it basically bullion.
Sorry you learned the lesson the hard way pennys. (Most of us have probably been there sometime). Even though Galt is quite brusque in delivery, I think ebay is not worth it either.