"Tailored" OCBD Shirts - Where?

Let me preface this with- I do not wear dress shirts daily for work.

Over the years I accumulated a bunch of cheap dress shirts with sloppy fits. My nephew got a new job, and needed dress clothes, so I passed a bunch down to him.

Now I would like to get 3-4 nice dress shirts. I am quite thin though, so would like to look into "tailored" or "custom made" shirts. Where is the best place to start, and how much should I be willing to pay for a decent shirt?