I charge 75p per bay with a min charge of £4 if theres an patio door to do i charge this as an extra £1.
I find you win on some small windows but lose on others but overall its about right, plus i use an pole ( which today has killed my arms

) which i tell the customer gets all the frames which it does.
Best thing to do is see what other window cleaners charge in your area and charge the same or near the same, as all area's are differnet.
Right off to rest my arm its killing me here, anyone get the same problem with a pole or is it just me?
Thanks
Justin