well,
$500.00 is about three hundred more than a shop will give him as a trade in but about $100.00 less than he could get were it priced for a quick sale. i don't see him realistically getting more than 650-700 for it unless it has some special feature (such as pinned and recessed or some special run or desireable commemorative) open the cylinder and see if it is stamped in the frame 629 or 629-1 or -2 etc.as previously stated some dash #'s are more desireable than others. other factors are, is the case a wooden presentation case or the cardboard box, are the tools and all papers in there. fwiw i got my 629-1 for 400.00 and was going to buy another about a year ago for about 550.00 but didn't get the funds together quickly enough. any how i don't think 5 bills is an insult(dealers will insult him if he goes that route) but it'd be a darn good deal on your end.
Regards,
Rich