Regarding prices- I'd recommend watching the auction sites because they show you what the guns are really going for on a weekly basis. I've pasted several links below. Of the three, gunbroker seems to have the best selection of modern firearms.
In an auction, you may find a nice deal from a private seller who is trying to sell an entire package gun, with mags, and accessories. I don't know about now, but a local shop (in Vegas) had a very lightly used, pre-ban, green AUG with its original box and accessories on consignment for $3200. It was in very nice shape. I do not know if it is still available, but you may want to contact the place if you are serious about getting one.
Black Talon. I just picked up a used USR ( this is the one with a grey stock, 20" barrel, no FH and thumbhole stock ) for $2350.00 shipped form an arfcom. member. I would rate its condition at about 95%. It came with 4 mags, sling and original owners manual. I haven't shot it yet but shouldering it compared to my FS2000 it actually feels slightly heavier. One thing I did notice was that extra piece of plastic in the thumbhole stock interfered with my right wrist while in my shooting position. That does bother me somewhat but for the money and it being a true Steyr Aug I couldn't turn it down. Only 3000 USR's were imported so it is somewhat a collectible. Just depends on how deep your pockets are...John