The three inch Model 10 bull barrel is a sought after gun. If it is a round butt, it's highly sought after. If it's a pinned roundbutt three incher, it's probably already gone. $350 is a bit high around here, but in some parts of the country, it would not be out of line.
That being said, I've yet to see a three inch Model 10 for sale. If I did, it would no longer be for sale, especially if it was a round butt.