But in a society that we like to claim is tolerant of all values, who are we to say that any of the buyer's values -- his motivations for making some choice --

But in a society that we like to claim is tolerant of all values, who are we to say that any of the buyer's values -- his motivations for making some choice -- are wrong in any objective way? Well, in the extreme cases there are things that society agrees are wrong, such as murder, theft, etc. Whether or not those are objectively wrong is a topic of much discussion in philosophy classes but society in general agrees they are. What we can often say objectively is that certain actions are detrimental to that person's stated goals. If your goal is to save enough to buy a new car with cash as quickly as feasible, then buying that piano at all is probably not smart, and doing so in the name of politness and civility is certainly contrary to his stated goal.