I agree with what the others have said, I don't
get insulted or offended when people offer low
(which most of the time they do).  I don't know
whether or not they are trying to low-ball me or
if they just completely don't know what the price
range is.

The only time I get a little annoyed is when
people email me :telling: me that I am going to
sell a cel to them.  But I always reply back to
them politely to tell them that I'm not interested
or the cel isn't for sale.