Have had this done several times for clients and for my own windows. Price depends on quality. There are cheap windows available from Leroy Merlin etc. if you are into diy.

Personally I use a local company who make the windows to measure. I had anti-theft glass fitted so I could get rid of all the metal bars - 2 layers of glass with a plastic film between on the outside pane and the same on the inside. You can hit it with a hammer and the hammer will bounce off - believe me I tried it - impressive, 10 times in succession before one of the panes of glass cracked! But you won't find this in Leroy Merlin.