Background check through a dealer is $10. (Tennessee Instant Check has to go through state DOSHS for current local wants and warrants before going through federal NICS, which means ATF does not allow Tennessee Handgun Carry Permit in place of the $10 TICS for a 4473 transaction at an FFL!)
Private background check, last I checked, cost $30 in Tennessee. That's more than the profit margin on a lot of private sales, swaps or trades. Most people don't use it, but rely on private judgement that the buyer does not appear to be a prohibited person, and the seller does not appear to be fencing stolen goods. Quite frankly, every Tennessee gun show I have been to has police presence doing safety check and cable tie on guns at the door,* and I treat rumor of undercovers walking the floor as a possibility. The shady transactions are least likely to occur at gunshows in my opinion (and according to the inmate surveys cited by Bureau of Justice Statistics). It's like the gun show attendees are prescreened compared to the folks responding to a classified ad or to the "gun for sale" word put on the street or bulletin board.
_____________________________________
* I was at a gun show when the a guy handed the cop at the desk at the door a gun he had inherited, had no use for, and wanted to sell it to an FFL. The cop doing the safety inspection and cable tie proceeded to eject a live round from the firing chamber and four or five from the magazine. Apparently the relative had died with the gun fully loaded, and no one else in the family knew diddly about clearing the gun. Similar situation at a gun shop involving a Winchester pump .22 rifle: an heir brought in an unwanted inheritance fully loaded, with no clue how it worked to even unload it himself. The more I think about those situations, the more I think next private sale or trade I do, I will limit myself to a fellow THCP holder for piece of mind.