thats the beauty of the window cleaning market, the prices can go from the sublime to the ridiculous. the skill is getting it as near to ridiculous as you can for your area.
I usualy walk around the property counting £1 per window (from toilet window to 3 section kitchen window)and doors. Dormers, skylights and patio doors at £2 each. Then i walk back round and look at the job as a whole to see what i think its worth. Bungalows same as mansions. hope this is useful