If you're not making a lot of power with lots of boost, a $30 cheapie from your local car store will be fine. In fact, a study done in AutoSalon magazine (I think 2007, can' remember issue) showed that 3A Racing (cheap no-name brand) had the best flow and filtration compared to other brands like Apexi, HKS, Trust, K&N, etc. I've heard since then that these cheap pods are not made out of a strong material, and the foam can get sucked into your turbo and engine under high flow.
Personally I use an Apexi Power Intake, sounds amazing and I don't notice a difference between other types of pods. In reality, there is probably <1% difference between all of them in terms of noticeable affect.