The Great Australian Two Dollar Coin Fraud

My own recent experiences with ebay have somewhat soured me on them as a legitimate source for coinage. I have become super suspicious of any potential purchase from ebay and due diligence is the key. Check the seller's feedback and number of sales. Also, how long have they been selling on ebay. You said it best, "Caveat Emptor" is the ebay buyers battle cry. ebay has no interest in screening such fraudulent listings. They are completely happy to make their money any way they can.

The main problem is, to quote Dilbert's Boss: "there's no law against optimism". It is not against the law for a seller to put up a coin (or anything else) for sale at a ridiculously high price. ebay does not generally prohibit people from making ambit claims as far as prices are concerned, and tends to assume that, if coins are selling for price X, then X must be the "true market value".

Now, coins do have certain restrictions on them, as far as what can and cannot be sold on ebay is concerned. One restriction is there is a limit of asking price of US$2500 for a "raw" coin (that is, a coin not in a recognized TPG slab). So yes, this listing does violate that policy - if it is reported, it should be removed. In theory, scammers should be restricted to list prices of US$2499, or use a coin that's been slabbed. That would help stop this specific listing and others in violation of the policy, but won't stop people from listing them for US$2499.

There's very little ebay could even theoretically do. To enforce some kind of "no ambit claims" policy, ebay would need to have some idea of what the "true market value" of an item is. That means hiring a whole bunch of experts to patrol the website and/or to review complaints and reports.

One thing they could do to minimize it, of course, is to go back to "the good old days" when sellers were charged a fee to put up a listing, and the fee scaled with the asking price of the item. But since it costs nothing for a scammer to make a bogus listing, they literally can't lose - and only need to find one sucker for a maximum payday. It's not entirely unlike phishing e-mails, in that regard.

Furthermore, it is fairly certain that at least some of these "selling a cheap coin for huge money" listings on ebay are posted by organized crime gangs, using ebay to launder their drug money or proceeds of crime. Listings like this particular one in the OP are probably not organized crime; those tend to not make any effort at all at explaining why a common circulation coin worth only a few cents ought to be worth $2500.

...Same happens here in the USA ... common coins for a ridiculous amount ... notice that the seller is new, with only one sale ... probably engaged in small-time money laundering, with the coin as a cover ... can't blame ebay for this, as they can't authenticate the asking price for every item ... coin prices are 'all over the chart', & who can say what one will pay for any given item? ... this is the ploy crooks use to disguise their exploits, as, legally, how would one prove fraud between a seller & willing buyer who doesn't complain ...
... about said site: Search "error" coin (any denomination) under 'SOLD ITEMS', sort the list by:'PRICE + SHIPPING: Highest', scroll through the list & notice the number of 1st -time / new sellers (zero to little feedback & sales history) who sell common coins at ridiculous prices ...
...I'm saying that it's not coins being sold here ... but that the listed coin is a legit cover for some nefarious dealings, with amounts of money too small for any agency to devote investigative time...
...This is done all the time in the arts & antiquities business, as well as other such where price is not 'set in stone' ... my opinion ...