How and where do y'all get your brake and shifter wires?

I feel pretty ripped off spending 20 bux for a set of 4 inners (2 brake, 2 shifter) and 12 feet of housing from my LBS everytime I want to replace the cables on a bike. I know where to find housing at a reasonable price, Where can I go to stock up on inner wires?

Also whats the advantage to Stainless Steel wires? less prone to rust?