What to do with very low offer on an item for sale

If recently listed it is either a bottom fisher, just someone who wants to play or someone using this tactic to get you to budge lower than you otherwise might.   For a new listing that is priced fairly, if it were me I wouldn’t entertain any counter offers but only state No Thanks and remind them its a fresh listing I will stick to.  Don;t even suggest a better price.

I sold my Hegel which was Mint but I used it several years.  I researched the price ranges and started with above average but not the highest.  A competitor listing had the same amp listed and as he came down, I came down. 

The listings sat for a time which doesn’t mean anything other than an interested buyer isn’t available at that time.   I finally agreed to a price that one consider absolute low especially for a mint but used amp and for a price the buyer came over to buy directly.   Doesn’t get any cleaner than that I suppose.

One year later, the same amp just sold for $400 more than I sold mine for but that’s how this is played.  Someone was willing to pay a higher price, presuming it actually went for that price.  That I would consider the absolute high at this point.

Outside of pricing something too high and/or someone asking for 10 to 15% off, much outside of that range isn’t viable to consider.  Some things, say inexpensive gear I get the price I ask, if its older and sits awhile, I may consider a discount that is acceptable to both parties.   

If you offer 10%, he/she may reject it but know how much you’ll drop today.   If they wait and it still hasn’t sold, they could come back and ask for a bigger discount.  

I would probably restate what makes this speaker a fair price, ask what kind of equipment they are using and perhaps to speak by phone before talking any price adjustments.  

I've been low-balled before and never entertain offering them a better price.  And I remember their handle.  

I have often observed that some think thier stuff has high value and your stuff has low value. Just like the old adage about thier manure not being malodorous. More to the point you get a percentage of supercilious sorts on this internet thing. Seller emptor too. 

I either don't reply or reply with a price *above* my asking price.   I take time to fully research the market for what I sell.  I write a very detailed description and include a lot of very clear, well lit, high resolution pictures.  I set my asking prices slightly above recent average sales, but not at the extreme high end.  Some may say my prices are aggressive, but I have received my asking price or very close 95% of the time.   I recently listed an item in several online sites and received a low offer from one person.  I replied with a higher price and did not receive a reply.   The items sold at my asking price 2 weeks later.  A week after the sale, the low baller sent another inquiry reiterating their original offer.  I replied that the item was sold for full price.  Person replied and seemed to be very surprised that my item sold. 

I've done a couple thousand online transactions (not all audio) and have begun to see this type of bottom feeder on the rise. Besides rage baiters or trolls, there are now a class of folks who send out dozens of responses a day, hoping to score one and then flip it.  I get at least one for every posting I do.

Facebook marketplace has recently added a "Deliberately Low Offer" to their list of things you can negatively report a buyer for along with things like "Scam" and "Didn't Show Up".  

Ignore or at the most say no thanks. You have no obligation to them and they clearly don't care about treating you honorably. 

I see the only thing you have listed in Marketplace is a twenty-year-old, 1/2 meter pair of Cardas Golden Cross interconnect, asking $400.00.  To me, it sounds like a lot, particularly its age and short length.

" I think that if (when) I offer more of my unneeded stuff, I shall know how to manage ridiculous offers.  How would a car salesman respond if I offered $20k on an $80k car?"

Am I assuming a used car?  Some new cars lose twenty percent when you drive them off the lot.  And a used car?  The variables of what a used car would sell for are infinite.  Seems like you have little experience selling anything, but you will figure it out.  My experience has been: You never know what will sell and what sits months without a bite.  I once got an older Marantz amplifier given to me, and it had an issue. I found out that an internal fuse on one channel would go up in flames(like a torch) when turned on.  I didn’t want to deal with it, so I put it up on CL, best offer.  I even had a short video of the flameout.  After putting the ad up, I was heading out maybe a half hour later, and for some reason, I checked the ad before I left.  I had a half dozen responses, some begging me to call them back quickly. Apparently, what I thought didn’t have much value had quite a bit of value, but back then, I didn’t know much about what was what in audio.