I would Say it would depend on condition and who is buying it. If it was minty and I was in the market for one (had the $$$) I would pay $900.00 - $950.00
If you can find the right guy who is a collector you might get even a little more. Presently there are a lot of factory refurbs going around for $750.00-$800.00 (with one mag) which is great for a guy who wants a Sig and is looking to save a few bucks, but for someone who knows what they want IE all original low mileage collector/shooter they are willing to pay the extra $100 to get what they want. That and you've got 2 mags. The zipperbacks were bringing a premium last time I saw, perhaps Sigboy might chime in here?