Well...that's a deep subject. Good windows are an investment. So let's talk quality then price.... I favor certain manufacturers because of quality. Marvin, Loewen, Pella are the top three. I need to look into Fensterman, a German company...but need a willing guinea pig. My house has Marvin... I recommend an exterior cladding of pre-finished aluminum and a wood interior. Marvin will do almost anything I ask...for a price. So if you want a Wineberry exterior with a walnut interior...game on. The size can be ordered to exactly fit the existing openings. Ergo, replacing means no rough opening framing changes. Interior and exterior trim will change....unless you use a Tilt-Pac. A replacement double hung sash kit that hangs in your existing frame...no trim change. Pella offers this option as well, but doesn't do EXACT sizes. Tilt-Pacs are a definite cost savings over tearing out the entire window.

The actual window cost is dependent on a lot of factors....in NorCal we have higher labor burden and higher wages than other areas of the country. Taking out a double hung sash and installing a Tilt-Pac should take about three man/hours on average. This includes the shifting of materials and tools, site protection and clean up. My crew bills out at $50 per hour. An average size Tilt-Pac, say 32wX48h, will be around $375. The larger the window the higher the costs. No cost benefit to smaller windows. Fixed windows or transoms, doors and sidelights don't work this way. Supervision and general conditions adds 10%, Add profit and overhead to the project...20% is a fair average. So for your house full of Tilt-Pacs...somewhere around $12 - $14K. Double that if sizes need to be bigger than the existing. Painting is not in this budget.

So none of that is real...because I am not in your area, not looking at your windows and not getting the specifications down for what you want. But it gives you a starting point?

Go to the local Marvin window supplier and have their salesman come out to measure the windows and discuss options (look on line at options first!). Talk to a local contractor, they are listed here on Houzz in the "find local pros" area. Pick three, get them in for a meet and greet. Get their labor rates and P&O percentage. Make sure they work with and have accounts at the window supplier. Do what feels right in selecting the one for the job. If none feel right...keep looking. Get a fixed price bid including the windows. Yes, you will pay more, but maybe less than 10%...and you have the peace of mind knowing that if anything fails in the first year, the contractor is responsible. Marvin's warranty runs longer....but they won't pay for labor if it is the contractor's fault. They are, however, really confident they won't have to pay for anything. I've had one warranty issue in 25 years of installs.