Jack, I've found that whenever I provide an over-the-phone appraisal, I will never get a chance to own that item. So what I do, as part of my business, is offer to give a written "Marketable Cash Value" appraisal and charge a minimal fee of $25. That way I at least get to see the item and my time is not totally given away to those that are just out there to steal from my wealth of knowledge for free.
I think we all cringe a little when someone asks "what's my xxx worth?", as they all want to hear it's worth millions, and very few believe us when we tell them the true value range.
Hopefully someone here will have a better answer than what I've been using, as we could all benefit from that.