Stop in for a cup of coffee

Talked to a buddy in Washington state yesterday. For 45 years he's owned a 1970 Boss 429. Hasn't really driven it in 40 years had 20K miles. Kept it running and cleaned up over the years. Anyway last week a guy approached him about selling it. Guy came by, checked it over, etc... He offered him 400K, and it sold.
I've looked up current ones selling and they are all 275-325K range. I didn't ask too many questions this time, but want to find out what made this one so special. He always said it was a special car, but I just thought Boss 429, ya it's special. Must be more to the story??
Payment $100 bills in a suitcase.