$250 is about right.
Depends on the details (specify MOP buttons!), cuff, choice of fabric, number of shirts ordered etc. I would strongly recommend trying the service and ordering one shirt to begin with before making a further commitment.
In my personal experience, since ordering with Charles I have not gone back to off the rack business shirts. He provides a great service and the quality of finished product is superior.
Great, thanks El Quag. Any tips for first timer?