Price on the SKS depends on its origin--Russian vs. Chinese vs. Yugoslav.  The latest Yugo's coming over have been selling for about $120.  The gun show dealers with the $250 Russian SKS's can't sell them because of the cheap stuff coming in.   Folding stock--again depends on who makes it.  You can get a cheap one from a gun show for $60.  So a fair price for your SKS might be as low as $150, as high as $225.  Military steel core ammo can be found for $79 per 1200 (or less, sometimes)--so maybe $30 for 550 rounds would be good, especially since you can get Wolf or other soft point or HP ammo for about $90 per 1000.