Price negotiations are just business. It's never personal. This is a free country and the buyer is free to make a low ball offer as I am free to not take it.
When I'm selling something, I have in my mind a bottom price I'm willing to sell it for. I'm going to ask more than that of course and give myself some room to give back a bit. Buyers always want to think they're getting a good deal and coming down on your price gives them that illusion.
Negotiating a purchase price is the same logic in reverse. I have in mind a top price I'm willing to pay for something and start out with a lower offer. I never low ball people, but there are times when my initial offer does get accepted.
Does it make sense to "ignore low ball offers"?
Assuming the person wants to sell the item and is accepting offers (since he didn’t say the "price is firm") then why say "I will gladly ignore low ball offers" ?
Why not make a counteroffer to the low ball offer? Thats how cars, houses and most anything that doesn’t have a "firm" price is purchased.
If its because the seller doesn’t want to waste their time negotiating they should say so or simply grow-up a little bit and not get so easily offended by a low offer. Besides, a buyer has no idea what the seller is willing to accept unless you negotiate it.
I’ve sold and purchased a number items after negotiating from a low first offer.