It's technology; technology *always* gets cheaper, :p. Unless you're trying to stay top-of-the-line on everything, which isn't necessary with miners considering they are only really running the GPU. FWIW, for miners you should be using an open steel case (like just beams) rather than a real case due to the heat.
Except that graphics cards have been getting more expensive due to demand. I bought my sapphire 7950 for 300 dollars a few months after they came out without even knowing what bitcoin is. Now you would be hard pressed to find the same card for under 500.