I don't know where you shop but my last delivery of 5.56 NATO (last week) was $305 including shipping. That was for 1000 rounds of Lake City 5.56 NATO.
Good to see the price coming down Lake city was going for $500 per 1000 not so long ago.
Where did you get that price?
http://www.ammoengine.com/find/ammo/.223_Remington_5.56x45mm