One of the best buys I ever made was a 3" 624 at my LGS a few years ago. It was absolutely filthy, inside and out, and I paid about half of what they were going for back then.

I disassembled it, cleaned it thoroughly, and refinished the grips. (Yes, it had the original finger-grooved combat grips.) It looks like new now, and shoots very well. If the LGS or the prior owner had taken the time to clean it, they could have gotten a much higher price for it. Go figure...