I'd sell it for $800. turn around and go to your local gun store and buy a new one off the shelf for $600-700.
unless you're a true friend, and you tell your buddy he's offering too much, and send him to the gun store to buy one.
my local store sells 92FS/M9s for $620 NIB. I think they ask 50-70 more for the INOX versions, when they have them in stock. in early January, I bought a new M9 from them, they had the display model, then went to the back to grab a NIB, never opened up piece to actually sell to me. opened it in front of me for the first time, just to verify the serial number on the weapon matched what was printed on the label on the box.
but then I went back a few weeks later with my dad to help him pick out his first handgun, and the only Beretta they had left was a beat up used 96D police trade in gun. (it was in INOX too...asking $500 for it, but had deep gouges in frame, broken rear sight blade, and damage to the crown of the barrel...looked like it belonged to a bike cop...and he dropped it while riding)
I've heard they are getting inventory back in though.