I get the majority of my generic flies (e.g., Adams, Elk Hairs, etc.) from Cabela's at $10/dz. I've found however, that when I take a trip, it's worth it for me to stop by the local flyshop and buy the local patterns, even if it's $2-3 a pop.
YMMV of course. I fish the Eastern Sierra every year. My mass produced patterns from Cabela's work just fine on a lot of the smaller streams and a few of the Mammoth Lakes. For fishing Crowley however, it's local patterns all the way for success.