Card shows
For vendors: show the evidence behind a price
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Buyers at a show increasingly check prices on their phones. As a vendor, it helps to know what they are likely to see and to be able to explain your number.
Know which source you are quoting
A catalog average, an eBay asking listing and a sold comparison are not the same thing. When you explain a price, say which kind of evidence it is based on and how recent it is.
Be clear about condition
Price evidence usually assumes a typical condition. If your copy is better or worse, say so. Buyers will check condition in person anyway.
Keep it a conversation
Evidence helps start a fair conversation. It does not guarantee a sale or a margin, and every vendor still sets their own prices.
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