You're taking your clients around to your carefully selected properties, just trying to get a good feel for the type of home they could see themselves living in and they ask about the fairness of the list price. You're understandably frustrated; after all, that step comes later. Here's how I recommend handling this delicate situation.
Answer: I can't possibly know off the top of my head, but when I get back to the office I'll do a CMA and share with you all the information so we can discuss it and make an informed decision together. It wouldn't be fair to you for me to just quote an estimate off the top of my head without doing any of the research. What we're doing here is narrowing down your list based on homes you see yourself living in, then we'll deal with the values.
Analysis: They usually find this to be a satisfactory answer as it proves that I'm honest and willing to do the work to provide them with the most accurate information, while also being willing to discuss their options with them and not just make a decision for them.