I've found several ways to reduce the cost. I work in miniature size, I tend towards using only one or two colors and I don't waste one little crumb of material. I keep everything in plastic bags, stored in a can I can seal. But even without the added stress of the current economic times our budget is pretty limited. I can't always run and get new clay when I want to.
So, what to do? I've applied to be a Polyform tester. I have a little experience since I tested the Shiva Paintstiks, and the bonus to being a tester is that you get to keep the free product you are testing. I'm also thinking of diversifying.
I've not been much into the bead making aspect of polymer clay, but my Google Reader has pointed me to some really great work and ideas out there. I've done wire wrap jewelry in the past (another costly investment) and with the right product at least I can make enough money to support my sculpting habit.
Creative thinking has to come into play in more than just your artwork, so if you're facing the same issues put your mind into other ways of making money as a sideline.