Well, too bad about the damage, looks like the seller missed one of the pieces of padding and if that correlated to where the damage is, then what it is worth comes down to what the two of you agree on. I would generally consider the front faceplate to be significant and worth maybe 20% so ~$200 off. You'll have to negotiate with the seller for what seems acceptable to both of you. For $900 I would consider it a good buy, for $1,100 in that shape I wouldn't.
Just my 0.02.
Just my 0.02.