Buyer submitted a "best offer" of $3. I counteroffered $12. She then counteroffered $12 to include shipping. I accepted that offer. Buyer then claimed that she had only ever offered $3 and used feedback extortion to try to force me to complete the transaction for $3. I offered to cancel the sale, and she left nasty negative feedback claiming that I don't honor accepted offer amounts. eBay reviewed what happened, confirmed that she had indeed submitted a $12 offer and removed the negative feedback. Whether it was an honest mistake or a clever scam, who wants to deal with someone who engages in feedback extortion?