I will answer your question but also want to throw an idea out.
Low ball offers are not unique to domain. Try listing a brand new $100,000 Mercedes on ebay and allow the make offer option without adding any restrictions. You might get 1000 dollar offers.
Ebay has setup the system great. It makes people up their offer while they are hot.
This is how it works.
When you list an item you could select to sell it at $1000 or make offer. You can then set an auto accept offer of anything above $700 and an auto reject offer of anything under $500. Anything between 500 and 700 you will get a notice to review with the option to counter.
If the buyer is hot for your item and he offered 300, he sees a noticed instantly that it has been rejected. Ebay might suggest a offer amount to the buyer that the seller will more likely accept.
The buyer is hot, he could up his offer right away and possibly automatically win.
Ebay limits how many offers you could make so you can't slowly figure out the lowest price.
How big companies do things is a gift for us to learn from. Ebay spent a lot studying how it is best to set things up. We should copy formats that work.
Currently the BIN make offer is not a good setup especially for impulse buys like domains.
To answer you question. When you get a low ball that is not close to your price you have to take a step back and remember this is a domain and unlike a car or watch there is no known price especially if the person knows nothing about premium names.
I used to get very mad at low ball domain offers. I do not get a lot of emails with offers and when I finally do its almost always a low ball. I wish the platforms would send you in the email subject a notice that "You received a low ball offer" because now the suspense builds and depending on the platform you might have to log in to view the offer.
Counter and educate is a good idea on dan. Counter and send a list of premium domain sales prices that sold and if you can show names like your that sold for 5x more include it.
Low ballers are not all people that do not have the money. Some are people that will buy but they want to know they robbed you, they want bragging rights, they want to tell their friends that they took charge, you wanted 50k and they warned you... and they told you... at first you didn't agree.... they want to tell friends that names like it go for 520k and they chewed you down to 30k. You were desperate, you are going through a divorce, a midlife crisis, you lost all your money in bitcoin or in stocks.