HI Rob
You will probably find, everyone prices different. I charge £1.50 a window for commercial. You could add an additional cost to this per floor.
e.g. ground floor £1.50
1st Floor £1.65
2nd floor £1.80 etc
Try it out, the only fear is you over pricing and not getting the work. However, if you can afford the risk, take it, at least you will know for the next time.
I have priced as high as £5 per window, purely because I didn’t want the work and still ended up getting it :-(
Andrew