It's basic supply and demand at each level: it filters down from retail to wholesale. As long as people are too impatient, lazy, or stupid to find those sources with lower prices... The expensive ammo "flies" off the shelves, thus validating the wholesalers' increased prices.
It's a cycle that winds down the same way: as ammo stays on the shelf longer at higher prices, the wholesalers are forced to lower their prices in order to unload their supplies. The cycle is also affected by competing manufacturers entering the cycle, see Tula's BrassMaxx, and the other new products that have cropped up at Walmart and other retailers.
I'm trying not to lecture, but this is Econ 101 and caveat emptor. The more poor souls buy ammo at higher prices, the longer the prices will be high. Period, end of story.
The only way to get lower prices is to let it sit there on the shelf gathering dust. There are other options available.
Okay, now I'm lecturing: Sorry, I will step off the self-inflated soap box now.