I was in 400 Jewelry & Pawn in Dawsonville yesterday and they had 1,000 round cases of Wolf (if you like Wolf) for $125. Dixie Guns in Buford (near mall of Georgia) has 1,000 rounds of Winchester White Box for $180. I'm fairly new to AR's so I don't know if these are good prices or not.
You could also try Georgia-Arms in Villa Rica, GA. Here's their price list. The first price is for 500 the second for 1,000.
223 Caliber / 5.56MM
Order # Item 500 1000
G223B 55gr FMJ $75.00 $139.95
G223C 55gr Soft Point $100.00 $190.00
G223H 52gr BTHP Match $110.00 $210.00
G223M 68gr BTHP Match $130.00 $250.00
G223A 55gr Ballistic Tip $145.00 $280.00
G223E** 55gr Ballistic Tip $190.00 $380.00
G223F** 40gr Ballistic Tip $190.00 $380.00
G223G 62 gr SS109 Green Tip FMJ $105.00 $200.00