Thanks everyone for your inputs and thoughts about the matter. appreciate it!
Yup its true that i told the buyer the estimated SC was 30k +/- cause seriously i don't keep track since i have two other DSLR cameras with me.
Plus i dont burst on the 1D thats for sure.
knowing that the actual SC was more than that, and without any doubt about it, I still replied with an apology and offered a small amount refund.
but I just couldn't accept a full refund of the camera body to me, and i have to return at least 4k back to him.
given the time period of 1week, a rental of 1D from reputable places will already cost at least 1,300 bucks.
and how am i going to sell the returned 1D?
I have been flexible from the start of the deal, giving in to the buyer's requested price, and even gave a lower price to the buyer since i couldn't include the neck-strap, without him having to ask me and traveling to his place from west to east to deal.
When such situation happened, I was quite tired to deal with it, yet i still replied.