PURE, I don't see WCing as a trade, just my opinion. They are skills, but you can learn pretty fast how to clean well enough to hold down your own round in a few days. The rest of the skill involed is learned as you go on. In a trade like plumbing, you are useless for the first few months I reckon. I don't think someone would pay you a plumbers rate to do all the plumbing in a new build with only a couple of weeks training, do you.
So that's why WCing isn't seen as a trade. To class your rate based on other trades seems unbalanced. I think that's the point Window Washers is making.
The point I would like to add about charging is, not all WC's start WFP, so looking at my setup, what would you do with my prices when I switched to WFP? Would you drop them 25%?
By the way, I'm not winding you up, just want to know if you see what I'm getting at.