There's certainly not anything wrong with selling MC pcbs, but there is something wrong with Riddle as a seller and a human being...
He's ripped a lot of people off in the past, especially with PC10 stuff. (Search, it's all there.)
You've also got to determine if it's worth dealing with someone who treats other members here on KLOV, even people he's never met, like this... http://forums.arcade-museum.com/showthread.php?t=202568