I can afford something if I want it strongly enough. An apple product is something I can never afford. A Louis Vuitton luggage is something I can never afford. The reason I cannot afford these things is because I don't see the value in these compared to cheaper alternatives. I think the people take the easy way out by saying that they can't afford it so that they don't get into an argument. Most people would stop probing further if you say that you can't afford it. It is a pretty smart move.