"What's Your Best Price?"

I agree w/ Tvad. The response to 'obo' should be an offer, not a 'what'll you take?' request.
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I agree with hwy61 as regards keeping the goal in mind, but as boa's hilarious link makes very clear, both buyer and seller should expect to participate in a little foreplay, even if the price essentially remains the same!

It's called "Getting to know yoooouuuu . . . . . . .,
getting to know allllabout you . . . . . "
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I still think it's all about foreplay. Go back and read this hilarious example. (Thanks Boa2)

http://www.mwscomp.com/movies/brian/brian-14.htm
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Has no one here on AgoN heard of, or used, PayPal's personal money transfer function? No fee involved! You don't get Buyer Protection on private sales anyway -- why pay for it?