The coins are genuine, the prices are not!
Coins listed in the tens of thousands even if sold, the buyers will not pay, then if the seller does not know how to retrieve their selling fees from a non sale, they will be lumbered with invoices in the hundreds.
They soon learn their lesson not to list items for ridiculous prices, but they break no rules, they can list for whatever price they like, sensible buyers can see the same coins listed for their true value and buy those.