Cost to install a new window?

This is a very broad question dependent on what kind of window, where its situated and if you're taking the old one out first. If you have good access then a window of average size can be removed in a matter of minutes, say about 20 min. A uPVC window can be fitted in about 15 to 30 min so long as its the right size and you don't have to start chopping away at brickwork or timber frame. the glazing , if its one piece with window trims is a 5 min job. Multiple pieces of glass will take longer, of course and if you're using putty then longer still.

I guess a fitter would charge between £100 and £200 or $200 and $400. plus the cost of your window. Plus the cost of any access equipment or scaffolding.

It is better to seek an advise of a person who professionally deals with windows and window products.