I picked up a job today (which may lead to more) because someone was charging too much.
I was asked to call on a lady who was a potential customer.
When I got there I had a look and decided on £9.
I tend to say £10 minimum now, but I'm doing next door for £10, and they have a small porch.
Seemed only fair, and it was actually only 7 windows, so I'd be done in under 10 minutes.
She then tells me she's got someone else coming next week, but he wanted £14!

Now if it had been the same or a pound more I may have said I didn't want to stick my nose in.
But if he's trying to rip people off on a 10 minute job, then I had no hesitation in saying give me a ring when you've spoken to him.
I wouldn't intentionally undercut, and I gave my price before I knew his.
But beware...those with daft prices, there's always someone who'll quote less and you'll lose out.