After that last round of price increases a few months back if you find Winchester or Remington under $10 per box of 25 it's a good deal. With another supposed to have happen first of year I doubt that price will hold now.
During 2007 I bought them as cheaply as $55 per flat of 250 for RIOs and paid as much as $100 a flat for Remingtons. Most commonly I paid $65 for RIO and $79 to $89 for Winchester AA and Remington Premier STS. But ALL of those were before the first round of price increases I've bought none since as I now have adequate hulls to reload what I'll shoot the next year or two.