Everybody gets clients like this and to be honest IMO its not their fault. They are constantly bing told through TV, commercials and shopping networks that they can have those 'salon results in the home'. Without technical knowledge about machines or detailed knowledge about products they dont know any difference and we cant expect them to know.
As a professional part of gaining and keeping your clientele is about showing them what they get from the professional treatments that they dont get from home treatments.
Some will get a little assy about it, but if you put your points across in a friendly way you can get around it. I find that by not outright disagreeing with them they tend to listen and never saying anything against where they buy their products. When they say they have found a way to do something, tell them thats great, but you do it this way because.....and they learn something.
Those that wont listen wont listen but the truth is if they really believed they could do it at home for nothing they would't be coming to you for a treatment
so you have already been victorious.