Does it make sense to "ignore low ball offers"?

Do you need to sell it? Are you desperate? If so then respond. If it’s a ridiculous offer I’ll respond with a higher amount than what it is listed for. Most of the time I don’t respond. House bids are different, the realtor has to submit the offer, but the seller does not have to respond. The buyers realtor will tell the buyer to make a bid good enough to get a counter to get negotiating started.

I don’t need to sell to buy what I want so I can sit on the piece for a while. Eventually everything sells.

Sometimes peoples expectations of a given price is unrealistic. Years ago I made an offer to a guy whose response was "go to hell". After a month or so he realized my offer was actually more than fair. He wanted to accept it. I told him that his "go to hell" attitude suggested that I take my business elsewhere.

As a prolific seller across a number of platforms for decades, lowball and BS offers are just a waste of time. If they are close, make a counter offer, but in my case I delete or ignore lowball BS, scammers, etc. If you are selling one item and rarely sell it's not an issue, but when you have multiple items listed and you have an endless stream of idiots sending lowball offers it's just not worth the time as these are NOT your buyers.

I respond to every offer I receive. If I find the offer really low, I will just say "No, thanks for your interest." If they are really interested, they will make a better offer. Negotiation can start from there. I have made more than one sale that way. If also helps to weed out people not interested in negotiating. 

On the other hand, I had one item for sale. To make the example easy, I am going to say the asking price was $1000. This item routinely sells for $1200 and more. The potential buyer and I haggled back and forth a bit and settled on a price of $850 with shipping split. I made arrangement for this person to pay and waited for some time and got nothing. I contacted the person and was asked if I would take $600 for the item. I told him we already had an agreed upon price. Crickets for a couple of more weeks and then he asks if I would sell for $500. I responded with, "For you, I will sell for $950 and you cover the shipping." Never heard from him again. The item ended up selling for very close to my original asking price, so it ended up working out fine for me at least.

Problem is many sellers inflate their price somewhat expecting that they will receive low offers and their prices will give them room to negotiate a fair price, so what exactly is a low ball offer. Earlier in this post a few mentioned 30%, certainly a low offer, but consider if a seller inflates his price by 15% expecting a buyer to ask for a 15% discount, as they routinely do, a  minus 30% offer could in fact lead to a successful conclusion at a fair price. I'm far less concerned with the amount of the offer than the manner in which it is conveyed.