It's all in how you say it

The owners of a wonderful luxury home often believe there are no properties which are comparable to their customized home.  So, when you arrive with your carefully prepared market analysis and begin to talk about comparable properties, they often are less than responsive to your information, because they are convinced there are no comparables.   

Consider changing your terminology.  Instead of comparable properties, use the term relevant properties.  For example, say, "These are the relevant properties with regard to recent sales."   Or, "these are the relevant properties currently on the market which buyer prospects may be considering along with your house."   A small change in terminology may help you overcome the objection that "nothing is comparable to our home."