Sellers Beware

sounds a bit like an severe overeaction! guy can’t change his mind ? i would not buy fr you thx! for heads up! 
as for shipping it is difficult
I joined pirate ship i get severe discounts on UPS almost 70% ! not so much on USPS also i have the seller give me their name address phone # e mail physical address and the outside dimensions of box  and the weight
then i BUY a free ( to them ) pre paid shipping label and e mail it to them all they need do is print it out ,tape it on the box(es) call for a pick up or drop off @ UPS store or hub
i pay for insurance for the full purchase price if the speakers or whatever are damaged I get the $.  otherwise if the seller pays, buys the label ,HE is insured! you are at his mercy to pay you the $ ( OK most will )  

My way, I get $ and pirate ship also refunds the shipping ! 100%
a claim is easy !
it all depends how they pack the speakers.
you need item like speakers well padded w/ bubble wrap then inside box ( you can get good cheap , new boxes at home depot  lowes or u haul ) you pad the outside of first box fully and put it inside 2nd box! you MUST double box and it is required by USPS you have to be careful the padding will not push a grille into a speaker cone ( like convex allison acoustics! )
even well and properly packed about 1/4 get damaged but i lose no $ as it is insured! ( pay for extra insurance )
UPS are crazy and will damage boxes drop them fr their shoulders onto the porch ( have it on camera !) USPS is more careful but usu too expensive .
fed ex is best but expensive . packing padding and double boxing IS the key you MUST double box! 
i buy some speakers ( always looking for AL series allison speakers ) " local pick up only "it is a serious PIA to pay a third party hired thru $5-7 ad on CL to go get the speakers  buy boxes packing material ( big bubbles is best ) and pad them send them
costs me an extra $50-100 !  I offer seller extra to box them up if he will  and i pay for boxes pack mtl etc 
i just shipped a used pair of allison AL115 fr Philadelphia, PA to Phoenix AZ cost me $100 for speakers $99 for shipping a 56 lb 25X25X 17 box $110 to pay the guy to get them,  box them up .  join Pirate ship save BIG $ 1
 

Somewhow he did not understand that if he makes an offer on A'gon, and it is accepted, he is obligated to follow through with the purchase.

When you make an offer on ebay, it is 100% binding, that is, your credit card gets charged and shipping proceeds the minute the seller accepts your offer. In other words, once your offer is accepted you can't change your mind. It's a very good system and Audiogon would do well to emulate it if they don't already.

Yeah these things happen. So as a buyer or seller beware.I bought a Macintosh amp and a Caver both worked like 3 months and died.I bought z turntable from a guy in came USPS.. damaged, it was no fun trying to get my money back.

The OP states that the potential buyer and he were communicating by email and that is where the offer was made, outside the audiogon format which is a bit telling in itself. The way Agon is set up with the make offer system actually locks the buyer into the offer made and allows the buyer and seller to the sell/purchase. Moral of story is, always inform any tire kickers that all reasonable offers will be considered but only if placed through the provided format. Enjoy the music

I have great luck with the USPS, but I rarely use them for larger items. By far and without fail, UPS has been the worst carrier I have used. It is getting to the point where I wont ship except on a pallet.