There is no way if you tried that here it would fly with customers, and that's in the north too. There is nothing illegal about what you are talking about, but I suspect now that your lying m8. I could be wrong but thats what I think. Also regardless of that.
If you came into my area, and did that to me, I doubt my customers would move over to you, but if allot did, and I was going out of business because of it, I would match your qoute, then put the prices back up when you disappear. I would also take or sent them a few of your qouts from this and regardless of the legality of it, the public and I suspect allot of the window cleaners on here would view you as a rouge, that wont last a minute.