I don't think that he's insanely rich. This statement that I received this morning says it all,
"Hi,
the car is still for sale, I tried to reach you but I was not able to get through.It has clear title, no accidents,runs perfect, you can pickup the car,or I can arrange shipping. let me know if interested because I want to get this done by weekend, I am selling so low, because this is my second car and I want to buy a viper,my dream car."

Thus, he is most likely some younger person who picked up a wrecked/totalled X5 and repaired it via cheap methods. Then spray it, detail it, and try to flip it. Otherwise, the trade-in value would be greater than $16,200 for his 'dream car' but I may be wrong.