11 years ago, I had all the windows replaced including a large custom Library window, a huge bay window (custom also) and a sliding glass door. I chose a window/siding/roof company that had been around for years, I knew their work and they used the same team to ONLY do windows- nothing else.
Top of the line then was $800 a window; had 17 standard windows and then the 3 custom, all with grids, all with a very very slight tint to block UVA. Windows were $450 a pop (special at the time), slider was $2500, Library (14 pane window) was $800 and the bay was $2200.
WORTH EVERY PENNY. No drafts and NO outside sound; couldn't hear the road crew outside jack-hammering 2 weeks later....found out when I went outside!
Do your research and pick carefully; take your time. Though cost is important, do not let it by your #1 reason to choose a company to do the work.