David MacNeil is not your typical billionaire. He did not make his fortune building social media apps, betting platforms, artificial intelligence software, rockets, crypto exchanges, or futuristic longevity treatments. He became a billionaire by selling car floor mats. Very, very good car floor mats. And now, thanks to one of the funniest billionaire real estate quotes in recent memory, MacNeil may have just entered the pantheon of great rich-gu…