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.