I had the exact same problem. Was talking to a potential end user on the phone and he had already found out the price on DL through this forum. I asked for 10x the price paid at DL and the end user was only willing to offer 3x. Luckily, I am now sitting on a much larger offer from another party.
In the interest of this community, which relies on selling domains, why not prevent Google from spidering the entire domains sold sub forum?