window cleaning is the same as any other business and it should be treated as such, for instance there are many different window cleaners, you have, Trad, wfp, domestic, commercial, shops only, cradle, abseiling.
Now all of these offer different services to their customers, some phone the night before, some don't, some collect the money at the end of the week and some don't, some clean the frames and sills, others charge extra for doing this.
Because of this and other things, all window cleaners are different, it is illegal to run "cartels" and price fixing window cleaning could fall into this catagory.
I offer a service but to my customers I sell my business to them first and foremost, price is a factor but to some its not the be all and end all.