+1 to iab's comment above.

Explanations for an offer level make sense in person (face to face, we give accounts of ourselves and our reasons for acting).

Money talks on ebay.

There is a wide range in what folks are willing to accept - some obviously don't actually want to entertain offers, but inexplicably leave the option open, whereas others will accept significantly less than the BIN. I've never had success trying to reason with anyone over why my offer price is reasonable, but I have got nice stuff from seemingly knowledgeable sellers for 30-40% less than listed BIN. Just make an offer and be done with it.