Good for Bad

Good for Bad is a Con Man's Tale that involves arranging a swap of something genuine for something bogus. You give me one dollar of real money for my counterfeit fifty. Better yet, if you have an art masterpiece I can get you a good replica for your insurance fire.

No art work? OK. I know a guy who has identical twin racehorses. One can really run, the other, not so much. He needs someone to place his bets for him, after he uses the slow horse to boost the odds, then swaps in the fast horse on the sly.

Not a gambler? Smart man! Hey I've got some British pounds here that aren't supposed to be in the country. Since you are going to London on vacation, howabout we swap for American, at about half the British face value?

What? No, man, nobody can counterfeit British money; it's too tough. I just want to avoid any embarrasing conversations with the IRS ...

Good for Bad always uses a switch. That is, the bad thing is swapped in for the good thing, without the mark knowing, often using sleight of hand or switching identical bags. The counterfeit money that is being sold looks so good because it is real money, but it isn't what goes into the bag at the exchange. The "fast" horse twin is the same horse, on drugs. The last time you ever see the real art masterpiece is when you give it over to be replicated.

Compare Pig in a Poke, which uses a similar Tale, but sells the item unseen.

General

 * The Ring Scam is one of the traditional good-for-bad cons. The con man offers to sell the mark a diamond ring for a few hundred dollars. The con man allows the mark to take it to a jeweller and get it examined—at which point the jeweller assesses the ring at much more than the asking price; it's a real ring worth thousands. The Mark's greed is turned against him, encouraging him to run outside and agree to the deal. The con man will use some pretext to get his hands on the ring, and switch it for a glass lookalike worth about five dollars, selling the worthless duplicate for his original asking price. An early version of this scam involving a gold-plated brass ring is known as "fawney rig".

Films -- Animation

 * Peewit in The Smurfs and the Magic Flute tries and fails to swap out one of the magic flutes for a fake.

Films -- Live-Action

 * Ocean's Twelve intended to do this to the Coronation Egg-swap out the real egg for a hologram-before a rival thief, Francois Toulour, beat them to it and won a bet.
 * Played with in the threequel Ocean's Thirteen, where Linus  swapped out Willy Bank's Five Diamond awards for fakes, only for Toulour to steal them from him.
 * In Catch Me If You Can, Frank Abagnale overpays a high-class prostitute with a phony check and receives his change in cash, effectively tricking a gorgeous hooker into paying him $400 for a night of testing the hotel's bedsprings.

Literature

 * This is used in the Discworld novel Going Postal, in which conman Moist von Lipwig views a real ring and a fake ring as part of his basic tools for emergencies. When the man wants to have it valued and they go to an actual jeweler he shows the man a real diamond ring. Reassured that it's real the mark then buys the ring, and when he takes it back to the jeweler to sell he's informed that it's brass and glass.
 * Happens to Bertie Wooster in the short story "Pearls Mean Tears". Fortunately Jeeves isn't as easy to dupe.
 * In Investment Biker, Jim Rogers remembers how in developing countries he would change money with black-market street vendors (who would give him fake notes maybe one time out of twenty) rather than official banks (who would take ten or twenty percent as commission on every transaction.)

Live-Action TV

 * In The Rockford Files, Jim Rockford uses one of these to recover a stolen pearl necklace. He uses a fake jeweler to convince the thieves that the necklace they stole was a fake, then convinced them to break back in and switch it for one that actually was fake.

Real Life

 * Truth in Television with any "traditional medicine" that used the parts of endangered species. For example, powdered rhino horn is considered an aphrodisiac. Not only is the claim bullshit, but they almost always use substitutes like cow bone for the actual powder. They always SHOW you the horn, but not the grinding process. And, unfortunately, this fact doesn't stop the poaching of actual rhinos for their horns.