Are we talking some sort of wtb post? An offer like $6250 isn't going to entice anyone not planning to sell his game to cash out. It seems like lots of want to buy types are extra cheap. It does hurt to offer too little. If someone annoys me with those types of lowball offers then I won't deal with them period.
Typically someone posting in a wtb scenario should expect to pay slightly more because he has to entice a seller that was not planning to sell to now sell. An extra cheapskate offer won't do this and just annoys.