Michael's numbers are correct, keeping in mind "start at" and that is for the window itself and does not also include a high quality professional installation, spray foam insulation, high quality caulking job, custom exterior cladding, etc. Installed - if you are getting a quality window from a professional window installation company that does't cut any corners and provides lifetime warranties on the product and workmanship and warranties on the glass breakage, etc - vinyl can range anywhere from $700-1,500 and fiberglass/wood clad $1,200-$2,500 depending on the features and add ons. Big box stores, subs, builders, etc would be a lower price point but you would not get the quality most people are looking for with a replacement project on the windows, workmanship, or warranty. Hope this helps.