If you don't know if it's worth 850, Why do you want it? Is there something about it that specifically attracts you? If you don't have a 'special' reason then it IS too much.
If I was buying another guitar I'd probably look at a Seagull first, an excellent guitar for about half of that. Unless of course I saw something that had special meaning to me.
When I bought my most recent guitar I used 'Peter's Placebo' - you know - "An ounce of image is worth a pound of performance". So I got me this really pretty bird's eye maple job. It sounds OK but LOOKS really great.