A hustle is really easy to spot, someone you don't know very well or at all will ask you to do something involving money. Usually something involving a little easy money for you.
In the case of the player trying to sell a large chip at a slight discount, or sports ticket, or slot ticket or any gaming instrument of value, there are many things that can go wrong for you if you take them up on the offer. The bigger the transaction is, the more likely things can go wrong and the more severe can be the consequence.
Things that can go wrong if:(I mean extremely wrong)
The chip is stolen. All large chips for sometime now have RFID chips in them. If you take a hot chip to the cage you are going to need to explain where that chip came from. If that chip was stolen in a violent manner, you may be asked many more questions then you can answer. You really have no way to know if that token was obtained in a legitimate manner if you got it from a stranger. And law enforcement is not going to easily dismiss your possession of something as being evidence that you were involved in the crime.
That player might be involved in a criminal enterprise that is laundering money. Actually selling a chip like this, to avoid a cash transaction with the casino, by definition is laundering, so by participating in it you have technically participated in a crime.
The first sign that someone is trying to hustle you is that they are offering some kind of gaming token at discount. There is no good reason for someone to not be able to cash out a gaming token if the token is legitimate. Someone making this kind of offer is trying to avoid something, like taxes or legal liability because the token is *found or stolen. If you take the person up on the offer, you become an accessory to whatever the reason is. You might be getting sandbagged, but your not going to get to play innocent victim safely.
*I mentioned found things. It is really not a good ideal to try and cash anything like large chips, slot tickets, sports tickets etc. that you may have found someplace. Your better off just turning them into lost and found (usually security) and take the upside of them being returned to you if no one claims them. In the casino this is not unwise to do with even cash. You don't know the source of anything you found and if it is stolen you have a problem. Slot tickets are often associated with the person whom had the slot card in the machine. Some place will press charges if you take a ticket out of machine that does not belong to you. I do not know what other things are tracked in this manner, but why find this out the hard way? Just never take anybody up on an offer of this kind. Even if your handicapped grandmother makes you this kind of offer, counter offer with I will push you to the cage.