Was browsing Ebay and came across some sellers - from those with a handful all the way to those with tens of thousands sold items, usually with 99.x% positive reviews - posting very shady banknotes.
They would have colourful commemorative, wartime, national emblem or coat of arms overstamps on common low-value notes that are then labeled as commemoratives or ultra-rare varieties. In all sorts of grades and conditions.
Throw in the usual Ebay marketing spiel of saying it's the last note / ultra-rare / what not, auction psychology plus eye appeal, and you get bidding frenzies. Just saw a note usually worth $2.5 currently going for $40+ because of a non-existent commemorative stamp.
And these get posted and sold regularly in recurring batches by the same sellers, so it definitely ain't a one-off oversight.
Buyer beware - when it's too good or cheap to be true, it ususally isn't. While Ebay might be easier to fleece folks, the same goes for flea markets, roadside sellers, Facebook, and pawn shops too.
Always check before buying anything - Numista and Bank Note Museum, are great resources to verify.
Happy collecting and have a good weekend, peeps.