True you can charge what you like but when you say your doing them cheaper than other WCs or doing them cheaper so they don't muscle in you are doing them for less than you usually would do,like you say that's up to you it's your work although it's not something I would do. I do 4 houses in a road I clean them for 2 1/2 times the other WCs charge they still stick with me,they even say I wouldn't expect him to do a proper job for that price they know how much he charges he's canvassed them but they won't switch,price isn't everything you get what you pay for.