The guy really doesn't get it does he. As soon as you start selling on price you get more and more people who further object to the already cheap price. He will be a carpet cleaner to the dregs of society.
Is it better in terms of fuel economy, chems and time to win 2 jobs out of 10 for a price of £500 or win all 10 totaling the same price? He won't understand this because he is clearly thick.
Your not in the margin game like a large manufacturer, so forget that concept. Your in the service industry where people buy trust, quality, reliability and likeability. You won't get more work charging less, you just open up a different sector of clients, that being - filthy poor dregs living in slum like conditions.