Very true! (about the switching costs of tailors) I use Poon Kee (upstairs along Wellington Street) and have done so for 15 years. I just had a suit made again by him - first one I've needed for 8 years (the quality is good enough that I'm still wearing stuff from 15 years ago) 5100 HKD, including two trousers, but the cost very much depends on the cloth you choose.

My wife keeps on wanting me to go somewhere trendier - but I just won't do it. But as he doesn't do shirts, I use Pacific Tailor (Pacific Place) for those.