Can an accepted offer be a lowball offer too?

I've never been asked to take something back but I have preemptively offered at the inkling someone might be dissatisfied was what I was trying to say. Both times i offered the buyer elected to keep the item in question.

Yeah, buying used on Audiogon is not for everyone, especially if you are not quite sure about how it would work in your system. In any case, if despite your best educated guess you make a mistake and got the wrong piece, just be prepared to sell it and maybe lose some cash in the process, but maybe not. I bought couple of wrong inexpensive pieces in the past here, put them on sale next day, sold in a few days , didn't lose anything on one piece, lost $100 on another. But I never bought or sold really expensive items.
Besides, people are spoiled by ebay where in many cases there is a possibilty of a return, and paypal is usually on the side of the buyer. But with electronics I often see no return policy there as well.

I had an interesting incident. Seller offered item and said first person to pay full price would get it sent to the 2 day shipping. I offered full price within minutes of posting but no response. 2 days later I was informed the item was sold. I complained to agon but no response .