At that price, I'd buy the gun and worry about the recall later, or more likely not worry about the recall at all. There's so much conflicting information out there on the 624 recall it makes my head hurt. As I alluded to in an earlier post, it either has something to do with bad steel or maybe that some cylinders got bored for .44 Mag instead of .44 Special. And maybe only one gun out of the hundreds sent back for testing failed the test, or maybe none did. And S&W apparently indicates a gun has been tested, and passed, by stamping a letter "C" on the box (on the box? really?) or they do something else (unspecified). If it was really something to be concerned about I have to believe the situation would be very clear, as is the case for the 586/686 recall.
After spending a few days reading everything I could about the recall with regard to my 624, I just threw up my hands and decided I'd shoot the gun and enjoy it, and that's what I do.
If you decide not to buy it, please PM me the name of the shop and I'll buy it. Or, if you want to make a quick couple hundred bucks, buy it at $550 and PM me.