Very often aftfer cleaning the windows the customer says STILL £12 etc I say yes (thinking is this an invitation, Should I put it up next time, but I only do if I think it deserves it. Normally I don't, probably too soft.). Do Sainsbury, Waitrose, Asda, Tesco etc never put their prices up? Of course they do. If u don't increase then u will be broke. The customers all understand this. If they don't ditch them.