Offer / counter-offer? Audiogon rules

the 48 hour rule is the reason I also never do counter offers...

One of the problems here is the obvious disagreement over VALUE.
In my completely unfounded opinion (CUO), the main weakness with bargaining is the implicit admission by both parties that 1) they don’t know how much it’s really worth and 2) they’re both out to screw every last penny out of the other guy. Some people really enjoy it, but most people don’t CUO. Some sellers must be feeling the squeeze by now but I guess their audio slush funds are tied to their stock portfolio and they can’t get off the pony. Used prices are too high. Half of MSRP is really a high price if it’s out of warranty.
Seems like that’s become the new “used list price.” Great for audio consultants in the dealer network who have used a new piece (on accommodation) for effectively no cost. 
So if your big power amp retailed for $2000, it should sell used for a maximum of $1000 for a #10 condition. Then, technological age and condition are the only problems. 

@denverfred 

One of the problems here is the obvious disagreement over VALUE.

Not sure why that is a problem.  The market will sort it out.  Buyers will pay what something is worth to them and sellers will adjust their pricing based on their level of desire to sell and their willingness to wait for a buyer who will pay their price.  That is the definition of free enterprise.

there's a distinction between an unofficial counter offer and an Audiogon rules governed official offer

"Austinbob"  in
my area if another buyer offers a higher price then other potential buyer(s) have the right to match the new higher offer.  Not lock in at their (lower) price.  See this happening a lot lately-a bidding war.  

As to the original post:

NO.  There are no remaining obligations on either side.   You declined his offer.  Case closed.  Negotiations are over.    

You are free to re-engage but that is a different discussion.