I just mailed a LLL.com owner (not too good letters...a q and an x in the name) a $3000 offer. This was, of course, just an opener and I was prepared to go upto 5-8k. The guy thought I was some lowballer ($3k for a lowballer? seriously..) and replied:
nice try dude. The price for this is 500,000
The response turned me off big time. The name wouldn't have fetched more than 6k here at DNF and I was prepared to go higher than that. But such a bad reply with a gung-ho attitude is just a put off.
So if somebody lowballs you, it would be better to keep the response polite. Many times they're serious buyers just testing the waters...