[RyanH]

Jon,
I have only done a few commercial windows, but they were in rather difficult locations. I charged something like $10-$15 per window. Each window was 4' wide x 6' high. The reason I charged so much was the safety factor. It only took about 1 minute per window, but it took 10 minutes to get to each window. I had to set up a ladder and secure it on a 50-60 degree slope beside the windows, which were 15-20 feet above the ground. Talk about stress-sweat!!!!
I sold it as part of a pressure washing job, so the total profit was pretty good. Like others have said, it is SO cheap to do windows. I use the ZEP tinted window cleaner because it is alcohol-based and evaporates very quickly and leaves no streaks.

I also do them for my residential customers, but I include it as part of the house-washing. I had (initially) some customers question why I had certain things that were included in the house wash and not others. Example: Gutters and siding, but not windows or trim. So, I now sell a total wash package. I don't give an option of washing the siding and not the windows. They never see the price breakdown. My final price may be a little higher than my competitors, but my customers like the fact that they don't have to worry about the final result. When I tell them all that is included in their price, it looks like (and is) a lot more than the local competition does!!
But, you asked for price. I usually charge around $2 for the bottom windows, up to $5-$10 for the upper windows. Size is generally not as important as convenience to me.

Ryan H.