Ricky-
As a member of this group, I can say that the way you did this deal is not the way we generally like to do business here at this club. This is a friendly group of honorable people who are loyal to the Alembic brand. Around here, it's generally accepted that the first person to respond to an offer for sale gets a fair shot to make the deal. While your actions may seem normal to you, and are certainly common when advertising through an independent site or in print, they are going to raise eyebrows here. You shouldn't sell the instrument for any price that makes you uncomfortable, but you should have honored the price you agreed on. If that wasn't enough, you shouldn't have agreed on the price, or you should have mentioned that you were seeking higher offers.
Additionally, we are always ready to welcome new members who share our interests. On the other hand, people who show up to seek a value for an instrument, sell it for max profit, and disappear again aren't becoming part of the community. As an outsider who just appeared here to make a sale, you have to expect that buyers would be seeking some protections in making a deal with you. It would be foolish in today's world to do otherwise, even more so since this appears to be a deal that will cross international borders. Some of us who have been around for a while can do deals in a more trusting fashion, but that trust must be earned over time.
Happy trails...