Last bulk package of 20 boxes of 20 (20 rounds per box) I bought cost me $80.00 at a gun show last summer (about $4.00 per box of 20).
$20.00/box? Maybe high end match grade stuff. At nearly $8.00 a box, I would say you paid bit more than you could have if you shopped around, but it has been at least 6 months since I bought any.
I usually just buy Wolf for my AR as it is usually the cheapest and these guns will handle it just fine. If I was a match shooter, I might buy something better, but a lot of people use Wolf for cheap plinking with no problems.
Purists flame away, but Wolf is plenty good enough to run thru my AR.