I would definately get design submissions from some of your friends (hey, like here at KH). They could e-mail you with their design and you could check through it, etc. It would be a page like Knitty.
As for yarn prices, check around other sites, and base your prices on those, same for needles. Are you making your own knitting needles or ordering wholesale from a manufacturer?
As for myself I'm willing to spend anything for a good needle, anything for a good yarn, and up to $5 for a pattern, but that's just me