Okay, let's think about how this happened. First, the buyer must not have known the seller. Otherwise the seller would surely realize that even a moron with mush for brains would figure out that an oven door was not a TV once it was opened. Second, the buyer was willing to pay $300 for a wrapped and boxed oven door, but not the $500 originally asked.
So, someone you don't know comes up to you and offers to sell you a flat screen TV for $500. You know this is a good deal, but can only get $300 together. The seller makes the deal anyway. You get a sealed box from the seller and give him the money without opening it up to find out whether you really got a great deal on a flat screen TV or whether someone just sold you an oven door.
Where are these people? I've got some magic beans to sell them.