LTLR is right about Dakota brass. It is spendy, but it's good brass and if you take care of it, you could probably get 30-40 firngs out of it, if you use bushings to size it and dont load it too hot. The 7mm and 330 (338) brass is made by Hornady and the 300 is made by Norma, so it's good stuff. But it's also about $1.65 a casing in lots of 100 or more. If you get 30 firings out of it, that's about $.06 per firing.
Mark