While I do not have info on James Chen, I do use another tailor at the Mandarin - A-Man Hing Cheong. I really think they have very high quality shirts and suits, and they are probably one of the most famous in the city. They can also recommend on style and trend. A shirt will probably run you for around $100 - $150 per piece nowadays, depends on the quality of the cloth that you use. They open till 7pm at night, so that should give you sufficient time to travel from the Lantau Island to Central by the MTR.