I've only left empty handed once. It was a Whitewater almost 20 years ago that was destroyed. Missing topper, boulders, side art on one side, smashed lock targets and ramps...just a wrecked re-import. This was before replacement parts were readily available and the guy was asking good money for the pin at the time.
In over 50 pinball and arcade game sales, I've only had 1 person leave my house without buying...and they did it twice. First time, I contacted them on a game they wanted and gave them a ridiculously good price since I got it for a steal. They showed up and it was apparent right from the get go they were not buying the game, even my wife could tell. Took the next hour going through all the menus, inspecting the cabinet and game with a flashlight and a fine tooth comb. Played a couple of games and beat around the bush. Finally they said it was exactly as advertised and they didn't see anything wrong with it...but they were going to pass because they thought they really wanted game xxx instead. Then after wasting my time for an hour, they asked to see the other games in my gameroom. WTF? Come to find out after the fact that this person had done this same thing with basically every person who owns a pinball machine in my area. Afterwards, I offered it to the second guy who contacted me and he was absolutely shocked the first person passed. He drove a couple hours the next day to pick it up and was beyond thrilled.
Lesson learned by me, right? No, I'm a nice guy and all about second chances, so when I was selling another game several months down the road below market value that this same person wanted, I reached out again and gave them first shot. They came over again...same deal. You could tell right away this deal is not happening and I was not happy this time. We do the same dance as before and once again they passed because they really wanted game xxx instead. I contacted the second person who wanted it, he came over a couple of days later and bought it problem free and was happy. The potential buyer is a nice person, but fool me twice, now...lesson learned. I don't even consider contacting that person again and haven't had a problem transaction since.