Firewire Cables

Is there any reason to spend $25-40 for firewire cables at various retail stores or are the $4-8 cables that I can find online as good? Seems like there is a racket out there pushing very expensive cables. Specifically, is the speed the same and is there really any risk of interferrence with cheaper cables?

Thanks

I recently ordered some inexpensive firewire cables online (and I'm talking $2.69 for 6ft cables) and they work just fine - no speed degradation and the connectors seem good. Of course, they were only available in one color (black) and the cable itself is a bit less flexible than some of my previously purchased more expensive cables (the shielding actually seems thicker on the cheap cables), but when I can buy 5 - 10 cables for the price of one more expensive cable, it became a no-brainer for me.