The price goes up as the windows go up (1st story, 2nd story, 3rd story...)...it also depends on size of windows, diffuculty accessing them (terrain or obstacles around building).
If it is similar to a 3X5 window then charge $2-$5/window for exterior, and double it for also doing interior. That would be my 1st story price.
But like I said there are a lot of other factors. You could also argue lowering that price per window since there are so many...its like your getting a bulk order...all your windows are in one place so you dont have to travel =). All depends....