Hate doing them so charge minimum 1.5 times outside price, sometimes double.
It's a hassle, got to take off shoes, applicator not too wet, watch out for dribbles and splashes, careful with ornamennts, move net curtains, blinds, etc. Then you always have a struggle reaching to top of the window above the kitchen sink!
We have quite a few who want this service but we try and only do it as infrequently as possible.
Saying that the lads have one to do today which we started last week and gave up on, its a beautiful new oak framed sun room, 12m x 5m with full glass on 3 sides.
However the problem is the builder has used something to seal the oak beams and they have splashed every window with the stuff. I don't know what it is but it took over 1/2 hour to do one pane of glass last week with some solvent cleaner and 4" scraper!! Gave up at that point.
I've now bought 4 bottles of Oilflo141 to see if that will shift it this week, I have re-quoted her £35/manhour plus chemical costs to do it, which she is quite happy with. The normal outside clean before this sunroom was built is £120 every 8 weeks.