Can't Believe This One!

I'd give 2000 for it
2000 cents

G'day,
quote: "It makes you wonder just how many of these sorts of items sell. It might be worth giving it a try ..."

I think the sums for this one look like this:
cost to set up scam: nearly zero
profit if scam succeeds: 40,000 %
whilst chance of success are small, it only needs to succeed occasionally, and the villain is well & truly rewarded.
If the note doesn't sell, he still has his $5.

For the un-initiated: polymer notes are difficult to counterfeit;
but they are still vulnerable to post-mint damage, which is almost certainly what has happened here.

Peter