Have you noticed that they seem to sell their bulk ammo in lots of 300, 600, and 1200? I think this is because shooters' minds are trained to think of ammo in lots of 20, 50, 500 and 1000 and don't automatically come up with price comparisons easily with the lot prices listed for the 300 and 600 lots.
It is pretty easy when the bulk amounts are in 500's to make comparisons with locally available boxes of 50. If you take the time to do the division correctly, the Cabela's stuff is often not really that great a deal. They are just hoping you don't take the time to really figure it out the per shot price.
As a side note, I have noticed that at some of the big box sporting goods stores the per shot bulk prices are often actually higher that the small box prices. This has been expecially true with some of the .223 ammo lately. I could buy it cheaper in the 20 box packaging that in the 50 box packaging (same brand).