Oh, this is rich. It reminds me of several incidents involving currency exchange on the streets when I lived in Russia from 1992 to 1996. There were plenty of scammers on the streets who would attempt to provide people with currency exchange, but often, they were just crooks taking advantage of naive people. I fell victim to this scam once, here's how it goes: the guy who says he will exchange your dollars for roubles take you to a somewhat secluded area. You hand him your $10, $20, $50 bill; he takes it, and folds it in half, then folds that in half again, so the numbers are concealed (FYI, this is the first sign to anyone with any intelligence to grab their money back and run). This is supposedly to "verify its authenticity." Then while you are looking at the guy folding the bill, someone else runs into him, or you, or both of you, maybe shouts something about "trading hard currency on the street is illegal!" The "exchanger" hands you back the money he has so cleverly folded, and hurries away. Upon unfolding your bills, you discover they have magically transformed into $1 bills. When the "bumper" comes along and interferes, the "exchanger" takes the opportunity of distraction to perform the currency switch.
This moron is obviously trying to fool someone who is incredibly stupid into believing the $20 is indeed a rare item. For me, the folded, crumpled quality of the bill sends up a BIG red flag, and the country the seller lives in is proof enough for me that this is a huge scam. I've seen some outrageous things on e-bay, but this really takes the cake!